B. The comma before the conjunction is missing.
You can see that this would be considered kind of a run-on sentence, and you know that you need to make pauses in this case. The real sentence would be:
My book is torn, and I want a new book immediately.
Now, you can see that this sentence makes a lot more sense.
In any case, you can eliminate the answer choices that don’t apply to the sentence. For example: A) The period at the end of the sentence is incorrect- is not the right answer because there’s always a period at the end of a sentence.
The same applies to the other answer choices.
Have a good day.