B. To provide a surface where exchange of gases takes place
14.
X and Y can complete a task in 28 days and 20 days, respectively. X started the task alone. After 4 days Y joined him till the completion of the task. How long did the task last?
There are five friends X, Y, Z, U and V. They are compared on the basis of height. Height of no two friends is same. U is shorter than Y but taller than X. Z is the tallest. X is taller than V. Who is the third tallest?