单项选择题

Unless astronomers ______ their search for extraterrestrial life to stars as exceptional as the Sun, they are wasting much of their time.

A．narrow down
B．boil down
C．tone down
D．let down
<上一题 目录 下一题>
热门 试题

单项选择题
After the students were shot by the military during a demonstration against the army ______, the girl students dared for the first time to stay out at night on the streets to picket.
A．control
B．ruling
C．government
D．regime
单项选择题
They eat a lot of meats and dairy foods, along with a lot of ______ items that don't fall into any Nutrigroup, such as sugar, fat, and condiments.
A．redundant
B．miscellaneous
C．versatile
D．trivial
相关试题