更多"Scientists have ------- for years t"的相关试题:
[单项选择]Scientists have______for years that turbulence within the gaseous clouds found throughout the Milky Way stymies star formation, but some of the forces behind this disturbance remain______.
A. (A) doubted … insufferable
B. (B) posited… unknown
C. (C) argued… relative
D. (D) assumed… exoteric
E. (E) conveyed … insuperable
[单项选择]Scientists have spent years into the effects of certain chemicals on the human brain, but with no result.（）
A. studying
B. researching
C. investigating
D. inspecting
[单项选择]Scientists and experts have proved that the pattern of a human being's finger skin ______.
[单项选择]Scientists have spent years_________ into the effects of certain chemicals on the human brain with no results.
A. studying
B. investigating
C. researching
D. inspecting
[单项选择]Scientists have discovered in the past few years that ______.
A. the exposure of DNA to the public is unnecessary
B. the tiny cell in DNA is a neat little machine
C. man actually knows nothing about DNA
D. man has much to learn about DNA
[单项选择]Only (within) the past 200 years (scientists have) found (out what) fire (is).
A. within
B. scientists have
C. out what
D. is
[单项选择]Now scientists have found in the past few years _________.
A. the exposure of DNA to the public is unnecessary
B. the tiny cell in DNA is a neat little machine
C. man knows nothing about DNA
D. man has much to learn about DNA
