A fill pipe can fill 1/2 of cistern in 10 minutes. In how many minutes, it can fill 1/2 of the cistern?  Choose the correct choice from the following:
A) 1 min	B) 4 min	C) 6 min	D) 10 min	E) 25 min

Rationale: "required time = 10 * 2 * 1 / 2 = 10 minutes answer is d"
Answer: D