Another name is voltaic battery
You need to use Planck's law:
E = h·υ = (h·c)/λ
Without making all the calculations, a fraction is bigger than another when the denominator is smaller. Therefore you need to find the smallest wavelength (λ) which is 450nm.
You could also be helped by colors: in order of decreasing energy, you have blue - green - yellow - red.
In any case, the correct answer is a).
Definition formula for momentum: P = mv
So P(A) = 0.45 * 50 = 22.5 kgm/s
P(B) = 0.45 * 80 = 36 kgm/s
P(C) = 0.45 * 25 = 11.25 kgm/s
B has the greatest momentum
