Primary succession occurs when a community develops while secondary succession occurs when one .

A. into a climax community; species replaces another

B. and replaces another; ecosystem becomes stable

C. on unoccupied ground; biological community replaces another

D. and then fails; niche changes

E. intraspecific competition; experiences interspecific competition

C. on unoccupied ground; biological community replaces another

Explanation:

Primary succession  is a gradual change that occurs on bare rocks or areas that have no life existing on it before. It could take several years to be colonized by living things.  

On the other hand, secondary succession are changes that occur when one biological community replaces another as a result of factors such as wild fires, or take place in abandoned farm land. New species of organisms take over the area that has life existing on it already. Secondary succession occurs on areas or land that has been colonized initially before.

option a is correct i.e.

explanation:

in context to the membrane of nerve impulse, the outer membrane of neuron is semi permeable that is only sodium ions can pass through the membrane i.e. smaller ions can pass through the membrane while larger ions cannot pass through it.