Answer:
1. What do you do <u>on</u> the weekend?
<u>On</u> Friday evening, we went to a party. We slept late <u>on</u> Saturday morning, and then <u>in</u> the afternoon we went shopping. <u>At</u> seven o'clock, some friends came round for a meal. We didn't do much <u>on</u> Sunday,<u> in </u>the evening we just watched TV. What about you?
2. I'll phone you <u>(no preposition)</u> next week <u>on</u> Thursday. It'll probably be <u>in</u> the afternoon, <u>at</u> about 3:00 p.m. OK?
3. I don't see my parents much. <u>(no preposition) </u>Christmas, usually and <u>on </u>the summer holidays.
4. <u>On</u> November 9th, 1989, the Berlin Wall was opened. For the first time <u>in</u> the late twentieth century, Germans could go from West to East Berlin without travel restrictions.
:)