Which describes how blood can be protective in nature?

a. by forming a protective layer within blood vessels
b. by carrying cells that defend the body from foreign materials
c. by secreting oil that destroys foreign materials
d. by producing acid that kills foreign materials

According the inverse square law, doubling the distance from the source of the sound, a speaker, for example, will drop the sound 6 db each time. if you were standing in the back of an auditorium, 32 feet away from a speaker not using any amplification, would you be able to hear a speaker clearly? why or why not?