Choose which planet you should write down if possible.
This sentence is intended for a student who has to answer a question on planets in a test situation IF he feels that he has been given sufficient information to make that call.
Choose which planet you should write down if possible.
This sentence is intended for a student who has to answer a question on planets in a test situation IF he feels that he has been given sufficient information to make that call.
It's not very well phrased, it's meaning is not at all clear. You are an English native speaker, so I'm not going to presume to rewrite it, but I feel that you should make another attempt.