Joker's Quote: "why So __?"

This page is the CodyCross answer for the clue below from Taking Care of Our Planet, Group 1573, Puzzle 4 (Recycling Plant).

Question is: Joker's Quote: "why So __?"

and the answer is: SERIOUS

Word Meaning:

SERIOUS — Without humor or expression of happiness; grave in manner or disposition.

Definitions from Wiktionary.

Joker's quote: "Why so __?" — CodyCross Answer | CodyCross Solutions