[ Grammar ]
Other radioactive elements ______ since: actinium (Debierne), radiothorium and mesothorium (Hahn), ionium (Boltwood), etc.
A. were discovered
B. are discovered
C. have been discovered
D. had been discovered
Random Topics:
Quantifiers & Modals of ObligationArticlePhrase and ClauseQuestion Tagand, so, but, becauseso vs suchPassive and Active SentencesWas & Were QuestionsPronouns of QuantityHelping and Linking VerbsOther quiz:
Conjunctions › ViewI’m playing tennis tomorrow … it’s raining.
A. if
B. unless
C. as long as
D. so long as
Grammar › View
what do you call a bunch of stairs
A. a flight
B. a flock
C. a troupe
Present and Past Tenses › ViewI … for two hours before I twisted my ankle.
A. climbed
B. had been climbing
C. had climbed
D. was climbing
General Knowledge › View
Which is the smallest ocean in the world?
A. Atlantic Ocean
B. Gold Ocean
C. English Ocean
D. Tiger Ocean
E. Arctic Ocean