**Rule**: The **Present Continuous Tense** is used to describe a current, ongoing trend or a process of change. **Correct Usage**: 'are melting' correctly describes the continuous, developing process of the ice caps disappearing. The subject 'The ice caps' is plural. **Incorrect Options**: (a) 'melt' (Simple Present) states it as a general fact. (c) 'have melted' (Present Perfect) suggests the process is complete. (d) 'melts' is a singular verb.

**Rule**: The **Present Perfect Continuous Tense** is used for a repeated, habitual action that has been happening for a duration of time ('for three years') up to the present. **Correct Usage**: 'have been going' correctly emphasizes the consistent, long-term attendance at the gym. **Incorrect Options**: (a) 'go' (Simple Present) is a habit without the duration. (b) 'am going' (Present Continuous) is for now. (d) 'have gone' would imply a single trip.

**Rule**: The **Present Perfect Tense** is used in negative sentences with 'since' to talk about a period of time that started in the past and continues to the present. **Correct Usage**: 'haven't heard' correctly expresses the lack of news from the point of her move until now. **Incorrect Options**: (a) 'don't hear' (Simple Present) is a habit. (b) 'am not hearing' is incorrect as 'hear' is a stative verb. (d) 'didn't hear' (Simple Past) is for a finished time.

**Rule**: The **Present Perfect Tense** is used to talk about past experiences that are part of a person's life, without specifying the exact time. **Correct Usage**: 'have tried' correctly refers to the life experience of trying various cuisines up to the present day. The subject 'We' is plural. **Incorrect Options**: (a) 'try' (Simple Present) is a habit. (b) 'are trying' (Present Continuous) is an action in progress. (d) 'has tried' is for a singular subject.

**Rule**: The **Simple Present Tense** is used for scheduled or habitual actions. The phrase 'once a month' indicates a regular, recurring event. A collective noun like 'board' is treated as a single unit, thus taking a singular verb. **Correct Usage**: 'meets' is the correct singular verb for the singular subject 'The board'. **Incorrect Options**: (a) 'is meeting' (Present Continuous) would imply a meeting is happening now or in the near future. (b) 'meet' is a plural verb. (d) 'has met' (Present Perfect) refers to a past meeting with present relevance.

**Rule**: The **Present Perfect Tense** is used for a recently completed action that has a result in the present, allowing a new action to happen. **Correct Usage**: 'have finished' indicates the work is now complete, with the present result being that the speaker is free to leave. **Incorrect Options**: (a) 'finish' (Simple Present) is a habit. (b) 'am finishing' (Present Continuous) means the work is not yet done. (d) 'have been finishing' is not a standard construction.

**Rule**: The **Present Perfect Tense** is used with the stative verb 'have' (meaning possession) to describe a state that started in the past ('since it was new') and continues to the present. **Correct Usage**: 'have had' correctly expresses the continuous state of possession over time. **Incorrect Options**: (a) 'have' (Simple Present) doesn't convey the duration. (b) 'am having' is incorrect because 'have' is stative here. (d) 'has had' is for a third-person singular subject.

**Rule**: The **Present Perfect Tense** can be used to describe an action that happened in the past and has relevance to a present or future event. While Past Perfect ('had studied') is also common here, Present Perfect can be used to emphasize the current state of her knowledge. **Correct Usage**: 'has studied' implies her knowledge of Spanish is still relevant now that she is in Madrid. **Incorrect Options**: (a) 'is studying' (Present Continuous) is for an ongoing action now. (b) 'studies' (Simple Present) is a habit. (d) 'studied' (Simple Past) is also possible but 'has studied' better connects the past learning to her present situation.

**Rule**: The **Simple Present Tense** is used to state a long-term, ongoing fact or trend. **Correct Usage**: 'continues' correctly describes the persistent, long-term trend of population growth. The subject 'The world population' is singular. 'is continuing' is also possible but simple present is excellent for stating a persistent fact. **Incorrect Options**: (b) 'is continuing' (Present Continuous) also works to show a current trend. (c) 'has continued' (Present Perfect) focuses on the past continuation. (d) 'continue' is a plural verb.

**Rule**: The **Present Perfect Tense** is used to describe a recent action whose result is important in the present. **Correct Usage**: 'has learned' indicates that the learning process has happened and the result is that the intern is now a valuable team member. The focus is on the completed achievement. **Incorrect Options**: (a) 'learns' (Simple Present) would be a general statement about the intern's ability. (b) 'is learning' (Present Continuous) implies the process is still ongoing. (c) 'has been learning' would emphasize the duration of the learning process rather than the result.