Six-Year-Old Jasper Has Learned That During a Thunderstorm,the Loud Thunder

Multiple Choice

Six-year-old Jasper has learned that during a thunderstorm,the loud thunder is preceded by a flash of lightning.He now covers his ears when he sees the lightning flash.What is the unconditioned stimulus (UCS) in this situation?

A) The thunder
B) The lightning
C) Covering his ears to the thunder
D) Covering his ears to the lightning