**Rule**: **Subject-Verb Agreement** combined with **Simple Present Tense**. The subject of the sentence is 'The number', which is always singular. The phrase 'of people who own a smartphone' modifies 'number'. The adverb 'every year' indicates a routine or recurring trend, which calls for the Simple Present. **Correct Usage**: Since 'The number' is singular, the verb must be 'increases'. **Incorrect Options**: (a) 'increase' is a plural verb. (c) 'is increasing' could describe a current trend, but 'every year' makes simple present a better fit for the repeated nature of the increase. (d) 'has increased' focuses on the result so far, not the annual recurrence.

**Rule**: The **Present Perfect Continuous Tense** is used for a repeated or continuous action that has been happening over a duration of time ('for the past hour') and has a present result or conclusion ('I think it's broken'). **Correct Usage**: 'has been making' emphasizes the continuous and worrying nature of the noise. **Incorrect Options**: (a) 'makes' (Simple Present) is a habit. (b) 'is making' (Present Continuous) is for now. (d) 'has made' (Present Perfect) is less likely for a continuous noise.

**Rule**: The **Simple Present Tense** is used to describe a predictable result or a habitual reaction to a recurring event. 'Every time' signals this repetition. **Correct Usage**: 'makes' correctly describes the consistent effect the movie has on the speaker. The subject 'it' is singular. **Incorrect Options**: (a) 'is making' (Present Continuous) is for an action happening now. (c) 'has made' (Present Perfect) refers to past instances. (d) 'make' is a plural verb.

**Rule**: **Stative Verbs**. The verb 'taste' is stative when describing the quality of something. It is used in the **Simple Present Tense** to describe a current state. **Correct Usage**: 'tastes' correctly describes the current quality of the coffee. The subject 'This coffee' is singular. **Incorrect Options**: (a) 'is tasting' is incorrect because 'taste' is stative here. (c) 'has tasted' is the wrong tense. (d) 'taste' is a plural verb.

**Rule**: The **Present Perfect Tense** is used for a past action that has a result in the present. **Correct Usage**: The past action is losing the keys, and the present result is 'I cannot find them'. 'have lost' correctly connects the past event to the present situation. **Incorrect Options**: (a) 'lose' (Simple Present) would imply a habit of losing keys. (b) 'am losing' (Present Continuous) is not logical in this context. (d) 'have been losing' (Present Perfect Continuous) would suggest a repeated action over a period, which is less likely than the single event implied here.

**Rule**: The **Present Perfect Continuous Tense** is used for a long-term, repeated action that started in the distant past and has continued up to the present. **Correct Usage**: 'has been knitting' emphasizes the continuous, habitual nature of her action over a very long period. **Incorrect Options**: (a) 'knits' (Simple Present) describes the habit without the long duration. (b) 'is knitting' (Present Continuous) is for now. (d) 'has knitted' (Present Perfect) focuses on the completed sweaters.

**Rule**: The **Present Perfect Tense** is used with stative verbs like 'live' to describe a state that started in the past and has continued for a long duration ('his entire life') up to the present. **Correct Usage**: 'has lived' correctly describes this long, uninterrupted period of residence. 'has been living' is also correct and emphasizes the continuity. **Incorrect Options**: (a) 'lives' (Simple Present) doesn't capture the duration from birth. (b) 'is living' (Present Continuous) suggests a temporary situation. (d) 'has been living' is also a strong correct option.

**Rule**: The **Present Perfect Tense** is used to describe an action or change that occurred at an unspecified time in a period leading up to the present ('since the new CEO took over'). **Correct Usage**: 'has doubled' correctly describes the change that has happened in this period and is relevant now. **Incorrect Options**: (a) 'doubles' (Simple Present) is a habit. (b) 'is doubling' (Present Continuous) describes a process happening right now. (d) 'double' is a plural verb.

**Rule**: The **Present Perfect Tense** is used to describe a state that started in the past and has continued over a period of time ('for years') up to the present. **Correct Usage**: 'has been unsafe' correctly describes the continuous state of the bridge over a long period, which has led to the current action of rebuilding it. **Incorrect Options**: (a) 'is' (Simple Present) only describes the current state. (c) 'was' (Simple Past) implies the state is finished. (d) 'is being' is for temporary behavior.

**Rule**: The **Present Perfect Tense** is used for a recently completed action with a present result (he can't find his keys), especially when counting the recurrences within an unfinished time period. **Correct Usage**: 'has lost' correctly reports the recent event. **Incorrect Options**: (a) 'loses' (Simple Present) is a habit. (b) 'is losing' (Present Continuous) is illogical. (d) 'has been losing' suggests a continuous process rather than a repeated single action.