Question

When turned about its axis of rotation, which shape could have created this three-dimensional object?

Answer 1

The first shape, or the triangle with its longest side bordering the line, could have created this three-dimensional object.

Answer 2

When a  body is rotating, there is a line that all the parts are turning about.  The parts farther away from that line travel on larger circle around that line, so they are moving faster.  Parts closer to the line follow smaller circles and move more slowly as a result.  Points right on the line do not travel at all.  

On the diagram you can see the greatest circle, formed by rotation. The points that form this circle are at the greatest distance from the axis of rotation. So you can see that only first or second options are true. But the second one is false, because the figure is not symmetric and therefore, formed shape must not be symmetric too.

Answer: correct option is A.