A is the answer to this question. AP is also known as Arithmetic Progression. This is a sequence of numbers wherein the difference will always be the same. This means that the in-between of the sequence will amount to the same number.

For example, when counting odd numbers by 2s, there will always be 2 numbers between the numbers in a sequence. Like 3,5,7, and 9. There are always two numbers in between. For this number, this means that it will be 1000, 2000, 3000, 4000, 5,000 and so on and so forth. This is an AP sequence because the number in between each number in the given sequence is the same.