**Answer**: (D) (4/3) hour

**Explanation**: Time taken by A alone = x hours (suppose)

Hence, Time taken by A + B + C = (x – 6) hours

Time taken by B alone = (x – 5) hours

Time taken by C alone = 2(x – 6) hours

Now, 1/(x – 6) = 1/x + 1/(x – 5) + 1/2(x – 6)

Hence x = 4/3