When they ___________ (open) their suitcases, they realized that they ...

★ Past Perfect Tense

When they ___________ (open) their suitcases, they realized that they ____________ (forget) their warm clothes.

A. open / forget

B. opened / had forgot

C. opened / forget

D. opened / had forgotten

Preview next quiz:

We form the past perfect with had and the _____ of the main verb.

A. affirmative

B. before

C. negative

D. past participle