If the shape in the [diagram] rotates about the dashed line, which solid of revolution will be formed?

a: shape 1

b: shape 2

c: shape 3

d: shape 4

Shape 3 will be formed

Step-by-step explanation:

Shape I is obviously the one obtained by rotating a single straight line around axis of symmetry.  In this case a cone or frustrum of cone is obtained.  But we have a funnel hence option I is incorrect

Shape II is got by rotating a trapezoid along with a line on top which gives the desired figure hence not right.

Shape 4 is got by roating a quadrant circle with another small quadrant circle on top hence incorrect.

Shape 3 is right because when we rotate the picture in the diagram around a vertical line we can get a funnel only.

THis is because straight line on top will give the cylinder part of funnel and down cone type will be given by the slant line.

Shape 3 is right

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