Must

The auxiliary verb must can be used to express probability or inference.

She must be about fifty years old.
You must have been mad to do such a thing.
She must have received your letter.

Note that in the sentences given above, must does not express compulsion or obligation, but inference.

Compare:

I suppose he is the oldest man in the village. (= He must be the oldest man
in the village.)

I think she is older than her husband. (= She must be older than her
husband.)

Can be + adjective

Read the following sentences.

He can be very annoying. (= He is not always annoying, but occasionally he is.)
She could be very intrusive. (= She is not always intrusive, but occasionally she is.)
Father can be very stern. (= Father is very stern at times.)

Do a lot of + gerund

This structure is used to emphasize the frequency with which we perform an action.

He does a lot of traveling. (= He travels a lot.)
I don’t do much traveling. (= I don’t travel much.)
I used to do a lot of gardening.
I have no time to do much gardening these days.
This old woman does a lot of talking. (= This old woman talks too much.)