Answer:
Option (c) is correct.
The Sine of an angle is the ratio of the opposite leg length to the hypotenuse length.
Explanation:
Given : The _____ of an angle is the ratio of the opposite leg length to the hypotenuse length.
We have to fill the blank with the correct option from the given options.
Sine of an angle is defined as the ratio of the opposite leg length to the hypotenuse length.

Thus, The Sine of an angle is the ratio of the opposite leg length to the hypotenuse length.