Which of the following are the natural barriers that keep infection out?
question 2 options:

a)

tears and skin

b)

masks

c)

mucous membranes and skin

d)

both a and c

how do pathogens spread?
question 3 options:

a)

indirect contact

b)

direct contact

c)

animal or insect

d)

contaminated food or water

e)

all of the above

Astudent wants to test the hypothesis that fertilizer improves the growth rate of grass seeds. to test this hypothesis, the student put the same amount of grass seed in 3 containers with the same type of soil. the student measured the growth at the end of the week. all plants received equal amounts of water and sunlight. if you were asked to graph this data, what would you place on the x-axis? a. fertilizer b. water c. plant growth d. week one