Answer: thatso

AnswerCrossword Clue
THATSO

"Really?"

THATSO

"Really, is ..?"

THATSO

Skeptic's comment

THATSO
"Oh yeah?"
THATSO
"No kidding!"
THATSO"Oh, really?"
THATSO"Oh, yeah?"
THATSO"You don't say"
THATSO"Honest?"
THATSO"Oh really?"
THATSO"You don't say?!"
THATSODoubter's remark