It is important to be thorough when you are answering reading comprehension questions. A big part of being thorough is checking that you’ve answered the question completely. Your teacher will only be able to grade what you’ve put down on the page, and you won’t be able to explain your answer by saying “well, what I meant to say was…”
Additionally, if you only answer part of the question, you might not get all of the points for that question.
A great way to be thorough is by checking your response against the original question. You might even try rephrasing the question as a partial statement and then use your answer to complete the statement.