Answer:
B. Sine.
Explanation:
We need to find the value of x which is opposite to the given angle (50 degree). Also we are given the length of the hypotenuse.
Sine = opposite / hypotenuse so we would use the sine.
Its worth committing this mnemonic to memory, which helps to find the required trig ratio:
SOH-CAH-TOA.
SineOpposite/Hypotenuse- CosineAdjacent/Hypotenuse-TangentOpposite/Adjacent.