**Answer:**

<em>Answer C. 5</em>

**Step-by-step explanation:**

<u>Product of Odd and Even Numbers</u>

Any number ending in 5 is necessarily a multiple of 5. For example, 85, 1005, 12345 are all multiple of 5.

Any number ending in 0 is a multiple of 5 and even therefore, is a multiple of 10.

Any integer number multiplied by another number ending in 5 gives one of these possible results:

* A multiple of 5 if the number is odd

* A multiple of 10 if the number is even.

The given product 1*3*5*7*9*11*13 is a multiple of 5 because 5 is one of the factors, and since the rest of the factors are all odd numbers, then the result is a multiple of 5 and has its last digit of 5.

**Answer C. 5**