What about 3? I choose A.

[v0031]

I'm thinking about what I'm going to do this summer.
      Maybe I'll get a job. If I get a job, I'll have ____money to buy some new things. I'd like to have some new dresses ____ I start school again in September. I can also buy some books or some music CDs. I really love jazz(爵士乐)．I could buy some more CDs____my jazz collection. Or I can use the money ____tennis lessons. I can play tennis ____，but I'd like to learn to play it much better. Or maybe I can use the money to pay for the piano lessons.I'd like to learn to play the piano，too.
　　  If I don't get a job this summer, I'll visit my grandparents in San Francisco. They live in a beautiful old house ____ the sea. My grandparents are always very nice to me. They'll let me sleep late. I ____ have to get up until 10 o'clock every day. I'll eat delicious food because my grandmother is an excellent ____.  She  always cooks my favorite food. I'll also go to the ____ with my grandparents. Because I like swimming in the sea. My grandparents like to go to museums but I don't enjoy it so much, so maybe I'll ____to watch TV.
1.A.less           B．many           C．a few          D．enough
2.A.because        B．where          C．when          D．if
3.A.for             B．to　           C．at             D．as

[v0031]

Again I think the question is not carefully designed.

[True Federalist (진정한 연방 주의자)]

Again I think the question is not carefully designed.

It's more like there often isn't any apparent logic behind English preposition use. Choice A is correct here, as one would buy CDs for one's collection, but one would add CDs to one's collection. The verb being used determines which preposition should be used.