Which of the following is not a prism ?
Correct option is B.
Because, a prism has a solid shape consisting of two equal ends, flat faces or surfaces and identical cross-section across its length.
$$A$$, $$C$$ and $$D$$ have two ends as square, triangle and pentagon respectively and their cross-section throughout is same.
So, option $$B$$ which is not a three dimensional figure is only non prism figure given.
The correct answer is option (b).