A boat B is moving upstream with velocity 3 m/s with respect to ground. An observer standing on boat observes that a swimmer S is crossing the river perpendicular to the direction of motion of boat. If river flow velocity is 4 m/s and swimmer crosses the river of width 100 m in 50 sec, then

• A. velocity of swimmer w.r.t ground is \[\surd 13\,\,m\text{/}s\]
• B. drift of swimmer along river is zero
• C. drift of swimmer along river will be 50 m
• D. velocity of swimmer w.r.t ground is 2 m/s