During which stage of sleep, also known as delta sleep, would a person have slow breathing and be difficult to wake.

a. between stages 1 and 2 of non–rapid-eye-movement sleep
b. in stage 4 of non–rapid-eye-movement sleep
c. near the end of stage 3 of rapid-eye-movement sleep
d. in stage 3 of non–rapid-eye-movement sleep

Ana is a hospital researcher. she wants to preserve organs for further study in a chemical that is called formalin. prior topreserving the organs, ana wants to familiarize herself with the hazards of using formalin. ana should consult formalin'sa. materials safety data sheet.b. date of expiration.c. date of manufacture,d. additional laboratory uses,