dv said:

A teacher, with a class of four pupils, writes the following words on the board.

VOWS
LASH
TADS
RIGS
LORD
FAKE
FORE
WAVE
AXES
BAIT
COVE
SCAM
PALS

He then writes one of these words on a piece of paper, tears it into four pieces with each piece containing one letter, and hands each student a piece, then tells them what he’s done. He adds, “I’m going to call your names in turn, and when your name is called, tell me whether you know what word I wrote.”

Teacher – “Amy?”
Amy – “Yes.”
Teacher – “Bob?”
Bob – “Yes.”
Teacher – “Carol?”
Carol – “No.”
Teacher – “Doug?”
Doug – “Yes.”

Carol, unprompted, says, “Then I can also say Yes.”

What was the word?

After lengthy thought, I think the answer must be RIGS, and Carol was handed the S.