What does the underlined modal auxiliary suggest in the following sentences (Q. Nos. 83 & 84) ? He must be at least sixty.

Question

Accepted Answer

The correct option is 1:
The modal auxiliary verb "must" can be used to express different concepts, including necessity (You must obey the rules) and strong obligation. However, in the context of the sentence "He must be at least sixty," it is used to express a logical conclusion or deduction, which is formally known as **Inference**. An inference is a conclusion reached on the basis of evidence and reasoning. When you use "must" in this way, you are saying that based on the evidence available (perhaps his appearance, his position, or information you have about his career), the only logical conclusion you can draw is that he is at least sixty years old. This epistemic use of "must" expresses a high degree of certainty—you are so sure of your conclusion that you state it as a virtual certainty, making "Inference" the precise term for this function of the modal.

The incorrect option is 2 (Probability):
While related, probability refers to a chance or likelihood, which is often expressed using modals like *may, might*, or *could*. "Must" expresses near-certainty based on evidence, which is stronger than simple probability. If the sentence used *He may be sixty*, that would suggest probability, but *must* implies a necessity driven by logic, not just a high chance.

The incorrect option is 3 (Conjecture):
Conjecture is an opinion or conclusion formed on the basis of incomplete information, often described as an educated guess. The use of "must" suggests a conclusion based on more substantial, observed evidence, placing it above the level of a mere guess or speculation (conjecture). Less certain modals like *might* or *could* would be more appropriate for pure conjecture.

The incorrect option is 4 (Belief):
Belief is a state of mind in which someone thinks something is true, often without definitive evidence. While an inference leads to a strong belief, the term "Belief" does not capture the logical process or the strong evidence-based necessity that the modal "must" conveys. "Must" specifically highlights the logical deduction that underpins the certainty, rather than just the personal acceptance of the idea.