1. Acceleration is the rate of change of velocity, so is the slope of a velocity vs. time curve (which you are given here). The curve is not a straight line, so its slope is changing. Points on the right of the curve are higher than points on the left, so the slope is positive. The appropriate choice is
... changing positive acceleration
2. Units conversion is required.
The appropriate choice is
... 0.673 m/s²
3. As before, the slope of the curve is the acceleration. This curve goes up less than 1 m/s for each second horizontally, so the appropriate choice is
... 0.6 m/s²