If two angles are complementary, that means their sum is 90 degrees
Let us draw a sketch to see the relationship between sine and cosine the complementary angles
Since , then
and
Since sinX = b/c
Since cosZ = b/c
Then sinX = cosZ
Since cosX = a/c
Since sinZ = a/c
Then cosX = sinZ
In the complementary angles, sine the first is equal to cosine the second
Since cos(X) = 9/11, then
Sin(Z) = 9/11
The correct answer is B