下列各项哪些不是空压机在加气站的作用（）。
A.提供吹扫用气
B.为加气站气动阀提供动力源
C.压缩天然气
参考答案：C
With the successful launch of Tiangong-I, which was ______ breakthrough in space field, China's space dream took a step closer to ______ reality.
A. a; / B. the; a C. a; the D the; /
无性生殖与有性生殖的本质区别是有无两性生殖细胞的结合。 （ ）
