Hermit Crabs Live in the Shells of Dead Marine Snails

Hermit crabs live in the shells of dead marine snails. When the supply of empty shells available to a hermit crab population was experimentally increased, the growth rate of the hermit crab population increased. This could be seen as evidence of

A) negative density-dependent population growth in the hermit crab population.
B) positive density-dependent population growth in the hermit crab population.
C) density-independent population growth in the hermit crab population.
D) density-vague population growth in the hermit crab population.
E) an imminent decline in the hermit crab population.