An object executes simple harmonic motion along the x-axis. As it passes through the equilibrium position moving toward +x, which combination correctly states the signs of its displacement x, velocity v, and acceleration a at that instant?
a) x=0,v=+,a=+
b) x=0,v=+,a=−
c) x=0,v=+,a=0
d) x=+,v=0,a=−