Question

A _________ engine operates using a three-sided metal rotor instead of the traditional piston-and-cylinder arrangement.

a. diesel engine
b. electric engine
c. LP gas engine
d. Wankel engine

Answer 1

That's a description of what makes the "Wankel engine" unique.

When it first came to the USA market, it came as the guts of a
new brand of car . . . the Mazda. I don't know if some, or all, or
none of today's Mazdas still use the Wankel 'rotary' engine.