Solve the following.

 1. It's multiplying by 2.

     3*2 = 6 | 6*2 = 12 | 12*2 = 24

 2. Each number is a multiple of 2

     2*1 = 2 | 2*3 = 6 | 2*5 = 10 | 2*7 = 14

 3. Each number is a multiple of 1.

     1*1 = 1 | 1*4 = 4 | 1*16 = 16 | 1*64 = 64

 4. Each number is multiplied by 7

     6 * 7 = 42

      #3 could be a multiple of either 1 or 4

the answer is b

he is going to fill two shelves and the third shelf will only have five video games