Irrational numbers are decimals that are non-terminating (don't stop) and non-repeating (don't have a pattern). So, if you were to multiply a non-terminating and non-repeating decimal by another non-terminating and non-repeating decimal, your answer will still be an irrational, non-terminating and non-repeating decimal that has no pattern and keeps going on and on without end. Choices B, C and D are all irrational decimals multiplied by a different irrational decimal so the answers would all be irrational. However, since A has the √11 x √11, we can simply this to (√11)² which is the same as 11, which is a rational number because it is an integer.