Two ants start moving simultaneously from two different corners on a

You are given the path and the speed of the two ants.

This means you do need the dimensions of the cube or the length of a single side to determine the distance between the ants.

Statement 1 gives you the dimensions of the entire cube, with the respective formulas you could now determien the distance between the ants.
However, at this point you could already stop as you have enough information to conclude that statement A is sufficient.

Statement 2 only gives you the vertical distances between the two ants, however unless you also know the horizontal distance you are not able to calculate the straight line distance.
Hence this statement does not provide information on its own to solve the question.

Due to statement 1 beeing sufficient on its own the correct answer is A.

Hope this helps.

Best regards,
Chris