He __________ on that invention for three years before he finally succeeded.
A. works
B. worked
C. has worked
D. had worked
Random Topics:
Simple Compound and Complex SentencesModal Verbs & Time PrepositionsModals in the PastPassive Voice & Verb TensesConjunctions, Interjections and Sentence TypeSubject and Verbs AgreementRelative ClausePrepositions after Verbs and AdjectiveModals for Necessity and SuggestionsGrammar - Present and Past PassiveOther quiz:
Infinitive & Gerund › ViewWe enjoy _______ to the beach on weekends.
A. go
B. to go
C. going
D. goes
Grammar › View
Check the underlined section. What is the role of it in the sentence?
The CD that Thomas scratched will no longer play.
A. Adjective
B. Adjective Phrase
C. Adjective Clause
D. none of these
Conjunction › View______she went home, she realized that her house had been broken in.
A. As long as
B. As far as
C. As soon as
D. As well as
Vocabulary and Sentence Structure › View
The manager assigned a difficult task to the new employee. He completed it successfully.
A. Completing the difficult task which assigned by the manager was successful for the new employee.
B. After assigned a difficult task by the manager, the new employee successfully completed it.
C. The manager assigned a difficult task to the new employee, but he completed it successfully.
D. The new employee successfully completed the difficult task assigned by the manager.