A 5-Kg Fish Swimming at a Speed of 1 M/s

Multiple Choice

A 5-kg fish swimming at a speed of 1 m/s swallows an absent-minded 1-kg fish at rest.The speed of the larger fish after this lunch is

A) 1/2 m/s.
B) 2/5 m/s.
C) 5/6 m/s.
D) 6/5 m/s.
E) 1 m/s.