To Find :
Which of the given pair of launch angles below will travel the same range given the same initial velocity.
Solution :
We know, two projectile with same velocity and different angles a and b can have same initial velocity on when the following condition satisfies :
a + b = 90°
Now, putting all the given value in above condition, we get for value 40° and 50° the above condition is true.
Therefore, option c) is correct.