The greatest straight-line distance between A and B would be the hypotenuse of a triangle with its height equal to the height of the cylinder and its base equal to the diameter of the cylinder. The height of the triangle would therefore be 5, and its base would be 2*radius, or 4. Using the Pythagorean Theorem, you can calculate the hypotenuse with hyp2 = 52 + 42, so hyp equals square root of 41, or E.