This looks like a homework assignment, so here is some general advice:
1. Using a collocations dictionary would probably help you find some of these answers.
2. Thinking about what part of speech is missing from each sentence will limit the number of likely choices.
3. Ignoring the given letter in the blank may help you come up with some possible answers and synonyms for those answers might be the "correct" one.
(For what it's worth, this looks like a poorly-designed exercise to me. If this is for homework, perhaps you could ask your teacher for some additional sentences with the same missing words blanked out: the more context you have, the more likely you are to be able to answer.)
I hope this helps.