When teaching the difference between auxiliary verb and linking verb, it can be pointed out that

• A. An auxiliary verb goes with a main verb
• B. A linking verb goes with a main verb
• C. An auxiliary verb cannot form questions
• D. A linking verb can be used as an auxiliary

Answer: (A)

The key idea here is how auxiliary verbs function with the main verb. An auxiliary verb attaches to the main verb to add tense, aspect, mood, or voice. It helps the main verb carry meaning about time or possibility, as in have eaten (present perfect) or is running (present progressive), and it often appears in questions through inversion or do-support. Linking verbs, in contrast, connect the subject to a description or identity in the predicate (She is a teacher), rather than helping to show when or how the action happens.

So the clearest teaching point is that an auxiliary goes with a main verb to express tense, aspect, or modality, while linking verbs serve to link the subject to a subject complement. There are nuanced cases where verbs like be can function as both, but keeping the distinction in mind helps learners use them correctly.