Nowadays extreme sport seems to have become all rage.

The incorrect part of the sentence is extreme sport.
Nowadays is a wrong answer because it is perfectly appropriate in the statement. As a result, this is an incorrect answer.
Extreme sport - is the correct answer since 'extreme sport' is incorrectly used here because the subject and verb agreement are not in the same direction, i.e., if the subject is single, the verb must also be singular, and if the subject is multiple, the verb must also be plural. As a result, the use of sport with severe is grammatically incorrect. It should be sportinstead of sports. So, the proper line is 'Nowadays extreme sports seem to have become allrage,' and this is the correct answer.
Seems to have become is an incorrect answer because seems to have become is a grammatically correct short sentence. Thus, we will consider this as an incorrect answer.
All rage this is an incorrect answer because all rage is the correct sentence. Here, all rage is used grammatically. Thus, this is an incorrect answer.