We _______ have a sports meeting this weekend if it _______.
A：won't; rains
B：will; rains
C：won't; will rain
D：are going to; is going to rain
It seems that it is going to rain. You'd better ________ the windows open when you leave the house.
2×0.7与0.2×7的结果相同，意义也相同。
① 细胞壁 ② 细胞膜 ③ 细胞质 ④ 细胞核 ⑤ 线粒体 ⑥ 液泡
