Which of the words/phrases (1), (2), (3) and (4) given below should replace the phrase underlined in the given sentence to make the sentence grammatically correct ? If the sentence is correct as it is and no correction is required, mark (5) as the answer.
The reason he has been so fat is because \(\underline{\text{because}\ \text{he}\ \text{never}\ \text{takes}}\) exercise.