Your answer is B. A heavy pack, for example is often more trouble than it is worth.
There are many stages in the writing process. When you edit, you want to check for style and conventions. In other words, you check for spelling and grammar errors. Another stage is revising, which would look more at changing areas of your essay, your voice, or your word choice. After you do your initial editing and revising, you will want to proofread to make sure you didn't miss anything before you finish the writing process.