An extremely loud noise awakens you; you emerge from sleep confused and do not remember the noise. You were most likely in which stage of sleep.

Question

a. Stage 1
b. Stage 2
c. REM
d. Stage 4
e. Twilight Sleep

Answer 1

And your choice is?

Answer 2

May I suggest you read your text materials, or, failing that, consult this:

http://www.sleepdex.org/stages.htm