Rule: Adverbs of Probability. The sentence requires a word to express probability. 'Likely' is an adjective or adverb meaning 'probably' and fits the structure 'are likely to have'. Option (b) 'like' is a preposition or verb. Option (c) 'alike' is an adjective or adverb meaning 'similar'. Option (d) 'likewise' is an adverb meaning 'in the same way'. 'Likely' is the only option that correctly conveys the intended meaning of probability.

**Rule: 'Debt' is an uncountable noun and is used without an article in the fixed phrase 'in debt'.** This expression refers to the state of owing money. It does not take an article. Therefore, 'no article' is the correct choice. Options (a), (b), and (c) are all grammatically incorrect for this idiom.

**Rule:** The Future Perfect Tense (will have + past participle) is used to indicate that an action will be completed by a specific future time. 'In five years' time' sets the future deadline by which the action of starting a business is expected to be finished. Options (d) is also plausible, suggesting the business will be in operation, but (a) focuses on the completion of the initial act of starting.

**Rule**: The **Past Perfect Continuous Tense** (had been + verb-ing) is used to emphasize the duration of a continuous action that was happening before another past action occurred. **Correct Usage**: 'had been working' emphasizes the long ten-year period of employment that occurred before the past action of his 'decided' to leave. **Incorrect Options**: (a) 'worked' (Simple Past) doesn't emphasize the duration as effectively. (b) 'was working' (Past Continuous) doesn't fit the sequence of events. (d) 'has worked' is a present tense.

**Rule**: The **Past Perfect Tense** is used for a past action that caused a subsequent past result. **Correct Usage**: The business 'failed' (past event) because the owners 'had made' a poor decision at a time before the failure. **Incorrect Options**: (a) 'made' (Simple Past) is also possible. (b) 'were making' is an ongoing process. (d) 'make' is a present tense.

**Rule**: The **Present Perfect Continuous Tense** is used to describe an activity that started in the past, has continued for a duration ('for five years'), and has a present result ('is very successful'). **Correct Usage**: 'has been running' emphasizes the continuous effort and management of the business over the five-year period leading to his current success. **Incorrect Options**: (a) 'runs' (Simple Present) states it as a fact. (b) 'is running' (Present Continuous) is for now. (d) 'has run' (Present Perfect) is also possible but focuses less on the continuous effort.

**Rule**: The **Simple Present Tense** of the verb 'to be' ('is') is used to state a person's current location or state. The phrase 'at the moment' indicates the present time. **Correct Usage**: 'is on a business trip' is the correct way to describe his current status. **Incorrect Options**: (b) 'has been' would be used with 'for' or 'since' to show duration. (c) 'is being' is used for temporary behavior, not location. (d) 'be' is the base form.

Rule: Business Vocabulary. Having a 'significant advantage over its competitors' because of a technology implies exclusive control or possession of it. 'Monopoly' means the exclusive possession or control of the supply of or trade in a commodity or service. This is the correct business term. Options (b) 'prohibition', (c) 'embargo', and (d) 'restriction' are all terms for limiting or banning something, which don't fit the context of gaining an advantage through possession.

Rule: Vocabulary from Examples. The examples given ('several mansions', 'a private jet') describe a lifestyle designed to impress others and show off wealth. 'Ostentatious' means characterized by vulgar or pretentious display; designed to impress or attract notice. This is the perfect word. Options (a) 'frugal', (b) 'austere', and (c) 'spartan' are all antonyms, describing a simple, plain lifestyle with no luxuries.

Rule: Business Vocabulary. The creation of a 'new industry giant' from two companies implies they joined together. A 'merger' is a combination of two things, especially companies, into one. This is the correct business term. Options (a) 'schism', (b) 'fissure', and (d) 'division' are all words for a split or separation, which is the opposite of what happened.