Fill in the blank with a suitable modal:
When I was a child I _________ drink a lot of milk.
A verb is used to express an occurrence, action, or state. It is the grammatical centre of the predicate in a sentence.
An auxiliary verb is a verb which gives is used in the formation of tenses, moods, tones, etc.
Option C is correct as was indicates use of used to.
The other options are wrong as no other tense can be used here.
The correct answer is C) used to