Antonym of GLIB

Answer: Option C

Glib : (of words or a speaker) fluent but insincere and shallow.
Unwilling : not ready, eager, or prepared to do something.
Hesitant : tentative, unsure, or slow in acting or speaking.
Dumb : temporarily unable or unwilling to speak.
Modest : unassuming in the estimation of one's abilities or achievements.

Antonym of Glib is Dumb