When he ___________________ (found) Microsoft, Bill Gates was only 20 years old.
A. found
B. founded
C. had found
D. had founded

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Pronoun Antecedent AgreementVerb Types and TensesGrammar - Verb Formsmust/shouldIf- ConditionalTime ConjunctionsTenses & PassiveGerund vs InfinitivePassive Modalsas...as, comparatives, superlativesOther quiz:
Grammar › ViewTense review. Choose the correct option according to the sentence: `When I …….at home, You ……. to school.´
A. arrived- left
B. arrive- has already left
C. arrived- had already left
D. arrive- leave
Phrases › View
‘haven’t heard from you’ refers to _____________.
A. haven’t hear you saying something
B. didn’t hear your voice
C. didn’t receive news from you
Grammar › ViewThe equipment I have ordered for the science lab _________ of five beakers, eleven test tubes and ten weighing scales.
A. consists
B. consist
C. is consisting
D. are consisting
Grammar › View
Today is holiday and these places of interest are open for free, so you _____ pay to get in.
A. mustn’t
B. mightn’t
C. shouldn’t
D. needn’t