A. Both 8 and 10 are even. Hence, 2 is also a common factor (other than 1) hence, not coprime.

B. 11, 12 only have 1 as a common factor. Hence they are coprime.

C. 1, 3 only have 1 as a common factor. Hence they are coprime.

D. 31, 33 only have 1 as a common factor. Hence they are cop rime.