Does anyone know the answer to this from tv's 3rd rock from the sun?

Which of the following actors appeared in every episode of '3rd Rock From The Sun'?

A) Joseph Gordon-Levitt
B) Wayne Knight
C) John Lithgow
D) Ron West

According to TV Tome, John Lithgow, Kristen Johnson and French Stewart appeared in every episode.

Welcome to Sitcoms Online, BTW.

Thanks for your help!

yea; cause I know it wasn't Wayne Knight; since he was also doing "Seinfeld" for part of the time that "3rd Rock..." was on.