Solution:
Given:

Since b and d are nonzero elements, then it is the product of two rational numbers.
Multiplying two rational numbers produces another rational number.
Therefore, the product is a rational expression.
OPTION C is the correct answer.
The answer is 10 because 5 10 15 20 25 30 35 40 45 50
It would be 6 haha I just took a test and got it right