Question

it was very early when he arrived at the cinema . add still work in the given sentence​

Answer 1

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For ten years' indicates that the activity has been going on for ten years and is still continuing. So, the correct form of the verb teach is 'have been teaching'.

Option A) had been teaching is in the past perfect continuous tense which means the action had been completed sometime in the past before another event. Since the sentence only has one event, we cannot use this option here.

Option B) was teaching is in the past tense. So this option is incorrect.

Option C) am teaching is in the present continuous tense but incorrect here since we cannot use this tense for the word 'for'. This is because the word 'for' implies that an action started in the past and lasted from the beginning to the end. 'Teaching', however, means that the action continues.

So, the correct option is option D).