by what factor would the rate of diffusion across a membrane change if both its area and thickness doubled

Size of particle.

Explanation:

Size of the particles that are diffusing is the factors that greatly affect the rate of diffusion. The rate of diffusion decreases if the thickness of the membrane becomes doubled while on the other hand, if the surface area of the membrane increases it doubled the rate of diffusion of the cell. If the size of particles is very small so it will diffuse if the membrane has double thickness.

meteorologists would compare a new weather map with one 24 h old to see how fast a front is moving.

the answer is d. chordata