When a man walks at the rate of 3 km/hr, rain appears to fall vertically. The speed of rain is $3\sqrt2$ km/hr. At what speed man should walk so that the rain appears to fall at an angle of 45° with vertical.

(A) 3 km/hr

(B) 4 km/hr

(C) $3\sqrt2$ km/hr

(D) 6 km/hr

(A) 3 km/hr

(B) 4 km/hr

(C) $3\sqrt2$ km/hr

(D) 6 km/hr