Why Would the Same Tone Result in Habituation for Rats

Multiple Choice

Why would the same tone result in habituation for rats exposed to a low level background noise and sensitization for rats exposed to high level background noise?

A) Only the high level background noise masked the tone.
B) Only the low level background noise masked the tone.
C) The low level background noise and tone combination activated the state and S-R system.
D) The high level background noise and tone combination activated the state and S-R system.