Some people _____ swimming and they think swimming _____ their health.
句意：一些人擅长游泳，他们觉得游泳对他们的健康有好处。be good at 意为“擅长”；be good for 意为“对……有好处”，故答案为选项A。
There are _____ and some bread on the table.
“两杯牛奶”要用 two glasses of milk，故答案为选项A。
We haven't got much _____ for our party. We should buy some this afternoon.
much 用来修饰不可数名词；根据本题语境可知，我们没有举办聚会的“食物”，我们应该去买一些，故所缺的词是 food。