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Answer is Right!
Answer is Wrong!
The correct answer is: for.
The baby is crying for help because they need something. It could be that they are hungry, tired, or need a diaper change. The baby is crying because they are not able to communicate their needs to the adult in the room, so they are using crying as a way to get attention.
The other options are not correct because they do not make sense in the context of the sentence. The baby is not crying of help, because they are not crying because of help. They are crying to get help, but they are not crying to help. They are not crying since help, because they are not crying because help has been given.