Which is the correct scientific notation for 724,000,000,000?

724,000,000,000 =  

Explanation:

To convert a number into scientific notation, we have to find how many digits are after the first digit so:

7, 2 4 0 0 0 0 0 0 0 0 0

11 digits are after 7

Meaning to make it into scientific notation, the power of 10 would be 11

i think the answer is a, hope this is right, that would be my best guess.

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.