If the new safety system _______ to use, the accident would never have happened.
A. had been put B. were put C. should be put D. would be put
People ______ better access to health care than they used to, and they’re living longer as a result.
A. will haveB. haveC. hadD. had had
Jim has retired, but he still remember the happy time _______ with his students.
A. to spend B. spend C. spending D. spent
The little problems ______ we meet in our daily lives may be inspirations for great inventions.
A. that B. as C. where D. when
The national park has a large collection of wildlife, _________ from butterflies to elephants.
A. ranging B. range C. to range D. ranged
In the 1950s in the USA, most families had just one phone at home, and wireless phones _______ yet.
A. haven’t invented B. haven’t been invented
C. hadn’t invented D. hadn’t been invented
