4个 $\frac{1}{6}$ 连加的和是____。

如图所示的几种情况中，a、b两点的电势相等，电场强度大小也相等的是（   ）

补全下面的短文。

    I had a good time last weekend．On Saturday morning，I____hiking with my mother．We climbed the mountain and____many pictures．For lunch，we____fresh fish in a restaurant．On Sunday morning，I played____with my cousin Sam．In the afternoon, I went____on the lake. It was fun!