我是小六毕业班的学生，做了很多练习，但是英语错题的错因没找到，请老师们帮我解析一下！（我在括号里填的是错误的）
1.（D ）Have you had ______lunch?---Yes,I had _____ good dinner at my friend's house, too.
A a/a B your/a C the/the D /,/
2.(B )Where are _________?
A. the officer's room B.the room of the officers Cthe officer's rooms Dthe office
3.(A)Hans,with his classmates, ________basketball every day.
A.play B.plays C.is playing D. are playing
4.---May I put the bicycle here? -----No,you_________(我填的是needn't)
5.（A）-----I am afraid I don't know.
-----_______
A.sorry. B.Thanks a lot. C.Thank you any way. D.You are welcome.
6.(B) ______eraser on the desk is Jim's.
A.A B.An C.The B.不填
7.(A)______turn is it now?
A.Who's B.Whose C.Who D.whom
8.(D)both my sister and my brother are ____
A.a police B. policemen C.policewomen D.polices
9.(A)----What are your two foreign teacher's nationlities?
-----_____.
A.They are Englishes B.They are Englisg C.They are England D.Thery are Endlands.
10.(D) Mr. White, with his friends, _______on a trip.
A.have B.has C.is D.are
11 (B) .----Show me the letter, please.
----Which one?The one ____ pencil?
A.in B.with C.by D.on
12.(D) There _____a parents' meeting tomorrow afternoon.
A.are B will have C.is going to be D.is going to have
13.(B) The teacher,with the students,____workonthe farm this Sunday.
A.is going to B.are going to Cis D are
14.(B)It's very nice_____you to help me.
A.of B.for C.to D.with
15.(B)---Have you had ____breakfast yet?
---No,not yet.
A.不填 B.a C. the D an
16.(B) What a cold day! Sam,you'd better _____ more clothes.
A.put on B.to put on C.take off D. to take off
17.(B) Dad,must I finish my homework today?
No,you needn't. You_____do it tomorrow.
A.need B.must C.can D will
18.(B)This is your watch. ______please.
A.Put away B.put on it C.Put it in D.Put it on
19.(D)Must they clean the classroom now?
No,they_____
A.can't B.needn't C.don't D.mustn't
20.(B)The food tastes_____but sells_____.
A.well/poorly B.good/ poor C.good/poorly D.well/poor
请各位老师看一下，帮我解析一下我的错题，最好能够提醒一下我哪里不足。谢谢了啊！如果好的话悬赏会很多的！