In order to answer standard form questions, think of it as simply needing to move the decimal place. 4.99 x 10 to the -3 is the equivalent of saying 4.99 with the decimal point moved three places to the left. Think of negative powers as to the left, and positive as to the right.
0.499 = 1 place to the left
0.0499 = 2 places to the left
0.00499 = 3 places to the left
Therefore, the answer is C (0.00499)