Problem Solving

Md.Nazrul Islam wrote:In the xy-plane , the line K pass through the origin and through the point (a,b)where ab (not equal 0)Is b positive .

1)The slope of line k is negative .

2)a<b .

(1) The slope of line K is negative implies b can be positive or negative.
No definite answer; NOT sufficient.

(2) a < b
If (a, b) = (2, 4), then b = positive
If (a, b) = (-4, -2), then b = negative.
No definite answer; NOT sufficient.

Combining (1) and (2), we know that either a = negative, b = positive OR a = positive, b = negative
Now a < b implies a = negative, b = positive, which implies certainly that b = positive; SUFFICIENT.

The correct answer is C.