[ Tenses ]
The extinction of certain species ____ scientists for years.
A. has worried
B. worries
C. is worrying
D. will worry

Random Topics:
Infinitive FormsSuch...that, so ......thatSimple and Progressive Verb TensesAdjectives Ed and IngSynonymWishes & Reported SpeechPast Tense, Recount Text, and Future TenseContinuous TensesModals and InversionImperative SentencesOther quiz:
used to vs be used to vs get used to › ViewI’m not used to ____ up this early.
A. get
B. getting
C. gets
D. got
Simile, Metaphor or Personification › View
The rained puddled at the door and washed anyone who entered with its splatter.
A. Simile
B. Metaphor
C. Personification