At an equilibrium position of a pendulum, the is at a maximum. a) displacement b) acceleration c) net force d) velocity

The equilibrium position is that at which the pendulum is at its lowest point; it is called this because, absent any other forces acting upon it, this is the point at which the pendulum would be at a stable, motionless equilibrium. It is also the point at which the pendulum, having been released from above, has translated its starting gravitational potential energy fully into kinetic energy. As such, this means that at this point the pendulum is at its maximum D) velocity.

The equilibrium position is the point below the pivot, at a neutral position. amplitude of the pendulum’s swing is the displacement from the equilibrium. each swing is referred to as maximum displacement or maximum amplitude. 

So your answer is D. Velocity

Answer (d) the universe had cooled enough for atoms to combine, protons and neutrons were too far apart to form nuclei;