According to the World Health Organization (WHO), people face health problems because of undernutrition and another people face health problems because of overnutrition.

Malnutrition problems in body

Explanation:

Malnutrition sustenance refers to inadequacies, abundances, or awkward nature in an individual's admission of vitality as well as supplements. The term ailing health tends to 3 general gatherings of conditions:  Undernutrition, which incorporates squandering (low weight-for-stature), hindering (low tallness for-age) and underweight (low weight-for-age);  Micronutrient-related ailing health, which incorporates micronutrient insufficiencies (an absence of significant nutrients and minerals) or micronutrient overabundance; and  Overweight, heftiness and diet-related noncommunicable sicknesses, (for example, coronary illness, stroke, diabetes and a few malignant growths)

option a is correct i.e.

only sodium ions can pass through the membrane.

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.