They say that a triangle has the length of one side as 6 and the second side's length is 7. The greatest area that those two sides could generate would be if they were at right angles to each other. If they were at right angles to each other, the area would be (6x7)/2, which would be 42/2=21. So the greatest area 6 and 7 can generate is the area of 21. So you cannot get to the answer at 3 of 24, but you could have less, so 13 is possible. So 1 and 2 are possible, 13 and 21, so your answer is D, 1 and 2 only.