Camilla Is an Insomniac

Camilla is an insomniac. She spends a lot of time in her bed watching television and doing homework, but she finds sleep elusive when she lies down there. Camilla would benefit from using her bed only for sleeping (or sex with her partner) because it has become a

A) discriminative conditioned stimulus for too many other activities.
B) secondary reinforcer for staying awake.
C) conditioned stimulus for too many other activities.
D) primary reinforcer for staying awake.