Question

If the given flat shape is revolved about the $Y$-axis by $360^\circ$, identify the solid that will be generated.

• A. A
• B. B
• C. C
• D. D

Hint:

For surfaces of revolution, walk the 2D profile vertically and translate: horizontal offsets $\to$ radii, steps $\to$ rings, and slants $\to$ cones.

Answer 1

The Correct Option is A

Step 1: Read the profile as radii.
On revolution about the vertical $Y$-axis, each horizontal distance in the 2D profile becomes a radius; horizontal steps $⇒$ circular ledges/rings, slanted edge $⇒$ cone frustum, and notches $⇒$ grooves (tori).
Step 2: Match features.
From top to bottom the profile shows: a thick rim (wide radius) $⇒$ a stack of three equal grooves $⇒$ an inverted conical skirt $⇒$ a small base boss. Among the options, only (A) shows exactly this sequence (thick top ring, three grooves, inverted cone, small base).
\[ \therefore \boxed{(A)}. \]