Four light waves are represented by
(i)
y=a1 sin ωt(ii)
y=a2 sin ωt+ε(iii)
y=a1 sin 2ωt(iv)
y=a2 sin 2ωt+ε.
Interference fringes may be observed due to superposition of
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iv)
(d) (iii) and (iv)