A mass–spring system is oscillating on a smooth horizontal surface. Immediately after the mass has crossed the equilibrium position and is moving towards the right, its displacement x is a very small positive value. With right taken as positive, which set correctly represents the signs of displacement x, velocity v, and acceleration a at that instant?
a) x:−,v:+,a:−
b) x:+,v:+,a:+
c) x:+,v:+,a:−
d) x:+,v:−,a:+