A:which
B:that
C:whe
D:whenever
在生物实验课上,小明想详细地观察洋葱表皮细胞结构,请你为他选择一种合适的观察仪器( )
She reached the top of the hill and stopped _______ on a big rock by the side of the path.
在比例尺是 的公路图上,量得云阳到重庆的距离约为4厘米,云阳到重庆的实际距离约是____千米.