Statement (1) is sufficient. It would require long division to determine the thousandths digit of 4/7, but since 4/7 is a specific real number, we should realize that we could do so.

Statement (2) is insufficient. Say that 100p = 112.11, for one example when the units digit is 100p is 2. We're interested in p, so divide both sides by 100:
p = 112/100 = 1.1211

The thousandths digit is 1--but remember that we invented that digit for the purpose of an example. It could just as easily have been any other integer. Choice (A) is correct.