Exploring ________space is exciting, yet dangerous. There is ________need for both robots and humans for space exploration.
#11641
A
the; a
B
a; a
C
/; a
D
/; the
推荐题目
 Almost _______ of the students in this class wear glasses, that is, _______ of them. 
#12037
A
two thirds; 60 percent
B
two thirds; 60 percents
C
two third; 60 percent
D
two third; 60 percents
 These flowers should not be watered too ______, once _____. 
#12398
A
long; every other day
B
often; every fourth day
C
soon; every two days
D
frequently; each five days