问题
选择题
Although everything seems to have been taken into consideration， accident can happen when the astronauts walk in space．
A．不填；the
B．an；the
C．the；the
D．an；不填
答案
答案：D
考查冠词的用法，第一空是泛指，所以用不定冠词a，第二空考查space前不加冠词，这类词还有nature,society,所以选D。