The first laser ——- in 1960 by Maiman almost half a century after the publication of Einstein’s theory of radiation which ——- the possibility of laser operation.
A. has been demonstrated / had shown
B. had been demonstrated / showed
C. was demonstrated / showed
D. demonstrates / was shown
E. was being demonstrated / shows
Random Topics:
Grammar - may/might/couldGerund or to InfinitiveTOEIC GrammarPerfect Verb TensesSimple Present and Present ContinuousGrammar: was/wereEnglish MorphosyntaxAdverbial PhrasesPast Simple TensePassive Modals, Impersonal PassiveOther quiz:
Grammar › View
The cat is :
A. in
B. on
C. near
D. above
Types of Sentences › View
Your brother and your friend broke the window in the living room.
A. simple
B. compound
C. complex
D. compound-complex
Vocabulary and Grammar › ViewHe is very ill, and the doctors are not sure whether he will _____ it through the night.
A. last
B. survive
C. endure
D. make
Gerunds and Tenses › View
. Which sentence shows a future plan?
A. I go to the doctor tomorrow.
B. I will go to the doctor tomorrow.
C. I am going to the doctor tomorrow.
D. I going to the doctor tomorrow.