Question

Answer the question to be a brainliest.

Answer 1

1) because it allows only some materials like CO2 02 nutrients etcc and don't send material like virus bacteria etcc

2)any object moving with varying velocity

3(to reduce the pressure and decrease the momentum and to reduce inertia

pls mark as brain list pls

Answer 2

1 - because it allows only selectively material like CO2
2 - any object moving with velocity
3 - because there is motion is present