sin4θ + cos4θ  in terms of sinθ  can be written as-

2sin4θ + 2sin2θ - 1 2sin4θ - 2sin2θ 2sin4θ - 2sin2θ - 1 2sin4θ - 2sin2θ +1

2sin4θ - 2sin2θ +1

If we put θ = 0° in sin4θ + cos4θ. it gives = 0 + 1 = 1 Take option D = 2×0 - 2×0 + 1 = 1 satisfied.