1. The fish I ate upset me.

Question

2. The fish I had eaten upset me.

(One more similar question, please. Are both OK? Because of the tense, #2 seems to be better. What about #1? Are both OK? Is there any difference between them?)

3.I had finished the work before my boss came back.

4. I finished the work before my boss came back.

(Between #3 and 4, which one is better? Are both OK as well?)

Answer 1

both of them are correct....
the difference is that one of them is in past tense and the other is in past perfect tense..
but you can use any one of them,its okay

Answer 2

Yes, you can use either sentence in each of the pairs, but if you are to be following the sequence of tenses strictly, then use only 2 and 3.

http://grammar.ccc.commnet.edu/grammar/verbs.htm#sequence ~~~> http://grammar.ccc.commnet.edu/grammar/sequence.htm