[ Past Perfect Simple & Past Perfect Continuous ]
I realized that I (forget) to thank them.
Which is the correct past perfect simple for the sentence above?
A. had forget
B. has forgotten
C. having to forget
D. had forgotten

Random Topics:
Nouns and QuantifiersLinking Words and PhrasesSimple Present and Simple PastMixed TensesModal and Modal PerfectVerbs + Infinitives / GerundsPresent Perfect Negative and InterrogativeMixed ConditionalSimple TenseTime and CalendarOther quiz:
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A. solvent
B. solute
C. solution
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Some of the rock that had been scooped out had also been __________ by the glacial action, turned into sand, and now made a small sand beach.
A. intervals
B. imbed
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Present Simple › ViewIt _______ here in December.
A. snow
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C. snows
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He _______ been at the meeting; I saw him in the office.
A. must have
B. could have
C. should have
D. might have
