If A, B and C together can finish a piece of work in 4 days. A alone in 12 days and B in 24 days, then C alone can do it in? Choose the correct choice from the following choices:
A) 1
B) 7
C) 8
D) 9
E) 6

Rationale: c = 1 / 4 - 1 / 12 – 1 / 24 = 1 / 8 = > 8 days ' answer : c
Answer: C