Help me please marks as

The correct option is;

(c)

Explanation:

The speed of light in a medium is calculated as follows;

Therefore, we have;

whichever one it is, it's definitely not one that you included on the list you provided.

here we know that ball will drop down by total distance 3.2 m

so here we know that

now using kinematics

now in the same time it will cover horizontal distance of 0.75 m

so speed of the ball will be