Read the following short excerpt of student writing. Use your vocabulary and grammar knowledge to determine which suggestions you would make to improve his or her grammar and word choice.

I really thought she loved me but I discovered her grave betrayal one afternoon. It was easy to figure out because she accidentally sent a text to me that was meant for him. I was confused by the text because it said, "Don't tell Mike." I felt insulted that she thought she could get away with this infidelity. At first I felt very angry bitter and hateful but then, I felt so hopeless and depressed. I longed for her to call me. I thought if I could just hear her pleasing voice, maybe then I would not be filled with such bitterness. Instead of calling her I talked to another friend who is good at listening and feeling my pain. Talking with her makes me feel euphoric. I think I may be on the road to recovery.

Which comma rule does this student need to apply to this passage?

I really thought she loved me but I discovered her grave betrayal one afternoon. It was easy to figure out because she accidentally sent a text to me that was meant for him. I was confused by the text because it said, "Don't tell Mike." I felt insulted that she thought she could get away with this infidelity. At first I felt very angry but then I felt so hopeless and depressed.

Use a comma to separate three or more items in a series.
Use a comma before a conjunction to separate two complete thoughts.
Use a comma to set off a phrase or clause at the beginning of a sentence.
Use a comma to separate coordinate adjectives.