The correct answer is
increasing velocity.In fact, the fact that the object has an acceleration different from zero means that the velocity of the object is changing. If the acceleration is in the direction of the motion, then it is a positive acceleration, therefore the velocity is increasing. The law of velocity for an object in accelerated motion is in fact

where

is the initial velocity, a the acceleration and t the time. When a is positive (same direction of the motion), then the term (at) is increasing as t becomes larger, therefore the velocity v(t) is increasing as well.