With the help of high technology, more and more new substances ______ in the past years.
#104082
A
discovered
B
have discovered
C
had been discovered
D
have been discovered
推荐题目
Mr. Chapman retired at 70 after he nearly 40 years with the Gas Company．
#102772
A
had spent
B
has spent
C
spends
D
would spend
Look at the timetable (时刻表). Hurry up! Flight 4026 _______ off at 18:20.
#101479
A
takes
B
took
C
will be taken
D
has taken
We are trying every possible means to ____ the people who are trapped in the ruins caused by this terrible earthquake.
#101467
A
recover
B
vote
C
rescue
D
guide
The first decade of the 21st century _____ the breathtaking and non-stop development of China.
#99973
A
witnesses
B
witnessed
C
will witness
D
had witnessed
The construction of the two new railway lines ________ by now.
#103148
A
have been completed
B
has been completed
C
has completed
D
have completed