Answer:
a). Toward us faster than the second object.
Step-by-step explanation:
According to the wave nature of light if the object is moving than its spectral lines will be shift.This shifting of spectral lines is known as Doppler effect.
if the two objects are moving towards each other it means that wave is compressed and the wavelength is shorter.Then the lines will be shift toward shorter wavelength if known as blue shift.
So the option a is correct.
a. toward us faster than the second object.