Following is the K-map of a Boolean function of five variables P, Q, R, S and X. The minimum sum-of-product (SOP) expression for the function is

A. $$\overline {\text{P}} \overline {\text{Q}} {\text{S}}\overline {\text{X}} + \overline {\text{P}} \overline {\text{Q}} {\text{S}}\overline {\text{X}} + {\text{Q}}\overline {\text{R}} \overline {\text{S}} {\text{X}} + {\text{QR}}\overline {\text{S}} {\text{X}}$$

B. $$\overline {\text{Q}} {\text{S}}\overline {\text{X}} + {\text{Q}}\overline {\text{S}} {\text{X}}$$

C. $$\overline {\text{Q}} {\text{SX}} + {\text{Q}}\overline {\text{S}} \overline {\text{X}} $$

D. $$\overline {\text{Q}} {\text{S}} + {\text{Q}}\overline {\text{S}} $$

Answer: Option B