Posthypnotic suggestion is mainly used to
a. prevent pain.
c. recall lost memories.
b. someone change a bad habit.
d. get people to forget their inhibitions.

Astudent poured a solution of bromothymol blue indicator into three test tubes. then he placed an aquatic plant in two of the test tubes, as shown below. he placed a stopper on each test tube and placed them all in the dark for 24 hours. bromothymol blue turns from blue to yellow in the presence of co2