The unit digit of the number $1 \times 3 \times 5 \times 79 \times 97 \times 113$ is
(a) 1
(b) 3
(c) 5
(d) 7
(e) 9
The correct option is (c).

The given product has one of its factors equal to 5, therefore, it is a multiple of 5, which always has the unit digit equal to 0 or 5. Moreover, since all the factors are odd numbers, the product is an odd number. Thus, its unit digit is 5.