[ Tenses ]
They __________ this research for years.
A. have done
B. have been doing
C. were doing
Select your answer:

Random Topics:
Family Vocabulary and GrammarFirst ConditionalGrammar - Present Perfect with for and sinceGrammar: MorphologySimple Future - WillConjunctive AdverbsGrammar - FuturePast ContinuousFirst Conditional & Future TensesAuxiliary Verbs & Question TagsOther quiz:
Grammar › ViewWhat is the present participle form of the verb “sleep”?
A. sleeping
B. slept
C. sleep
D. sleeps
Present Perfect and Simple Past Tense › View
………. you ……… the grocery shopping today? (do)
A. do-have
B. has- done
C. have -do
D. have- done
