Given the position function, the velocity function is obtained by taking the derivative:
The velocity is increasing its own derivative is positive, so we also have to find the acceleration by taking another derivative:
To find when , we first need to know where
:
The quadratic factor is always positive (its discriminant is negative), which leaves one solution at . To either side of
, we have, for instance,
which indicates that is increasing for
, making the answer A.