Answer : acceleration , a = g = 9.8

Step-by-step explanation :
Projectile motion is the motion of an object projected into the air, that is subjected to only acceleration due to gravity.
When a projectile is fired, the velocity have two components i.e. x and y. The x- component of acceleration is zero because the speed is constant. But in y- direction, the acceleration is constant i.e. g or 9.8 m/s^2.