Given below are two statements:

Two Sources ${\mathrm{S}}_1 \mathrm{and} {\mathrm{S}}_2$ of intensity $I_1 and l_2$ are in front of a screen [Fig.(a)]. The pattern of intensity distribution seen in the central portion is given by Fig.(b).

In this case, which of the following statements are true?

(a) $S_{1}and S_2$ have the same intensities
(b) $S_{1}and S_2$ have a constant phase difference
(c) $S_{1}and S_2$ have the same phase
(d) $S_{1}and S_2$ have the same wavelength 

1. (a, b, c)

2. (a, b, d)

3. (b, c, d)

4. (c, d)