75－17－39=____

阅读材料，完成下列问题。

材料一：我国各地降水量季节分配很不均匀，全国大多数地方降水量集中在五月到十月，这个时期的降水量一般要占全年的80%。以北京为例，降水量集中在夏半年（4~9月），占年雨量的90%以上，冬半年雨量不足10%。

材料二：我国600多座城市中，有三分之二供水不足，其中六分之一严重缺水，所以节约用水尤为重要。

A: Hi, Linda! Did you buy lots of things at the grocery store (食品杂货店) yesterday?

B: Yes, I did. But I would like to go the supermarket to buy things.

A: What's the d____ between a supermarket and a grocery store?

B: A grocery store is s____ than a supermarket. In a supermarket I can buy many different kinds of foods.

A: So you have m____ choices (选择) in a supermarket than at a grocery store.

B: Yes, you're right. I often shop in Smith's Supermarket. It's the b____ supermarket in our city.

A: Oh, I also want to go there tonight.

B: What do you n____?

A: I want to make a fruit cake for my daughter, so I need cream, eggs and some fresh fruit.

B: OK. I need a few things too. We can go together

如图所示的电路，当开关 S 闭合后，电流表测量的是通过____（选填“电源”、“L₁”或“L₂”）的电流，电流表的指针偏转如图所示，电流表的示数为____A．