HELP PLS What is the purpose of the valves in the heart?

a. To control how fast the heart beats

b. To separate the heart into two sides

c. To keep the mood flowing in only one direction

d. To prevent pathogens from entering the heart

How is health different for most people in this country today from what it was for people born in 1900? a. people have a shorter life span. b. people today work harder to survive. c. people today live in poorer sanitary conditions. d. people today can focus less on day-to-day survival and more quality of life.

How are people today protected from poop 50 points

Which of the following represents a difference between viruses and viroids? a) viruses infect many types of cells, whereas viroids infect only prokaryotic cells.b) viruses have capsids composed of protein, whereas viroids have no capsids.c) viruses have genomes composed of rna, whereas viroids have genomes composed of dna.d) viruses cannot pass through plasmodesmata, whereas viroids can.