Which of the relationships listed is a consumer—producer relationship? A. grasshoppers eating grass
B. roadrunners eating snakes
C. snakes eating toads
D. toads eating grasshoppers

the answer would be A. grasshopper eating grass

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.