there is an error because -9 x 1 = -9 not -1. But I would assume that you multiply -9×-1 and then -9×-2 ect.
Answer/Step-by-step explanation:
A. 
Using b = 2

Using b = 4

Using b = 6

Using b = 8

Using b = 10

Using b = 2

B. 
Using x = 3

Using x = 5

Using x = 7

Using x = 9

Using x = 11

Using x = 13

C. 
Using a = 2

Using a = 3

Using a = 4

Using a = 5

Using a = 6

Using a = 7

D. 
Using y = 2

Using y = 3

Using y = 5

Using y = 10

Using y = 8

Using y = 6

All of them are, except ' π ' (pi) ... which gives you an idea of why
that one is usually written as a symbol and not as digits.
Here's a useful factoid regarding the other numbers on the list:
-- <em>ANY</em> number that you can write down on paper, <u>completely</u>,
using digits, is a rational number.
Are you doing formulas????????????????