Hi Nitesh,

Its kinda function question.

The function defined here is a “round-down” function. That is rounding down to the nearest integer.

For example,

[2.5] = 2

[3] = 3

[-1.5] = -2

Question: [a] + [b] = 1  ?

Statement I is sufficient:

ab = 2

So we could take a = 1 and b = 2, in that case rounding down of 1 and 2 is 1 and 2 itself.

In that case, [a] + [b] = 3, So answer to the question is NO.

Lets take some non – integers  for a and b, lets say a = 0.5 , b = 4, in that case rounding down of 0.5 and 4 is 0 and 4.

In that case, [a] + [b] = 4, So answer to the question is again NO.

So whatever the values you take, you still get the answer here as NO.

So sufficient.

Statement II is insufficient:

0 < a < b < 2

So, we could take  a = 0.5 and b = 1, in that case rounding down of 0.5 and 1 is 0 and 1 .

In that case, [a] + [b] = 1, So answer to the question is YES.

Also we could take,

 a = 1 and b = 1.5, in that case rounding down of 1 and 1.5 is 1 and 1 .

In that case, [a] + [b] = 2, So answer to the question is NO.

So insufficient.

So the answer is A.

Hope this helps.