Question

I knew I must tell this man the truth (pick out the modal auxiliary verb and state its function)

Answer 1

Answer:

I knew I must tell this man the truth.

must- Modal auxiliary indicates compulsion.

Answer 2

Answer:

In this sentence, the modal auxiliary verb is 'must'.

Explanation:

.Modal auxiliary verb can be used for showing capability, necessity, possibility or willingness. In simpler words, the verbs are full of possibilities.  

.Some of the examples of modal auxiliary verbs are can, could, may, might, must, ought, shall, should, will, would, and so on.

.We can also indicate the modal verbs as negative forms ‘may not, might not, should not, etc’.

.In the given sentence, ‘must’ is the modal auxiliary verb used, as ‘must’ is the form of necessity.