The walls of the alveoli and capillaries are permeable. What does this mean?

Options for the question have not been provided. They are as follows:

Substances can pass through them

They are made of muscle

They are located throughout the body

They are made of bone

Substances can pass through them

Explanation:

producers: apple trees, potatoes, carrots, grains, acorns, cabbage, grass, corn, lettuce

consumers: deer, mice, rabbits, chickens, squirrels, horses, worms, cows

predators: eagles, frogs, wolves, owls

silt loam

hope this