Read the sentence. the astronomy club placed the telescope on the tripod and that was their choice. according to the elements of style, which sentence is the best revision? it was chosen by the astronomy club to place the telescope on the tripod. the astronomy club chose to place the telescope on the tripod. placing the telescope on the tripod was chosen by the astronomy club. no change

The best revision is the following one: "The astronomy club chose to place the telescope on the tripod". By selecting "to choose" as the main verb, you can avoid using the coordination in the example (and that was their choice). What is more, there is no point in using the passive voice as in B and D because the agent, the doer of the action, is recovered by the by phrase (by the astronomy club).  It would be grammatically incorrect to say the following:

*Placing the telescope on the tripod was chosen

You clearly need to recover the doer of the action.  With passive constructions, this is not strictly necessary because the action performed is more important than the person doing it. That is why the agent is suppressed.  As this sentence is not the case, the passive construction is not the best revision.  

explanation:

you only need simple sentences to answer this. just answer these questions.

what do you think annie thinks of the mother? do you think annie believes the mother is a fit mother for helen.

what about the father? what would annie think of him? she might not like him, but does she respect him.

how about the son? would annie think he is the only voice of sanity in an insane place?

what about helen herself? this is the key question. how does she see helen? what do you suppose she thought her first job was going to be.

these aren't hard questions. just state the obvious. annie is not that well educated: she just knows what she has to do. write it that way.

you can do it if you've read the book or seen the play or movie.