Fill in the blank with a suitable modal:
________ careful! You are making mistakes.
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 A is correct as careful indicates the use of be which suggests of a state.
The other options are wrong as no other tense can be used here.
The correct answer is A) be