[ 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:
Modifiers › ViewThe flagman motioned the car right.
A. adjective
B. adverb
Pronoun-Verb Agreement › View
____ build a campfire after dark.
A. She
B. He
C. We
D. It
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