Is it b?

10^3 = 1000 and .01^3 = .000001 [remember this simple rule, when you are multiplying decimals, your answer has to have the total decimal points from all of the numbers multiplied. So, here you have 2 decimal places and you are multiplying them 3 times, 2 * 3 = 6 decimal places to the left.]

1000/.000001 = 1,000,000,000 or 10^8 [in the denominator move the decimal places over to the right until you have 1. As always, do to the numerator what you do to the denominator. Since you moved 6 decimal places over in the D, do the same in the N and you will end up with 1,000,000,000/1 which is just 1,000,000,000].

Hope I am right.

Solution:
10^3 = 1000
0.01^3=0.000001
1000/0.000001 =1000×1000000=10^3×10^6 =10^9.

Crap, counted my places wrong. The lesson? It's better to use the exponents rule.

the simplest approach would be

(.01 ^ 3 )a = (10^3) ...... we are asked to find a !

(10^-6)a = (10^3)

a = 10^9

thanks
Senthil