Answer:
Preventing the spread of disease-carrying insects.
Step-by-step explanation:
The health can be maintained at the personal and public level as well. The personal maintenance of the health includes the personal hygiene, avoid eating contaminated foods and water.
The maintenance of the public health s quite important for the prevention of the disease. The disease spread can be best prevented by killing or prevent the growth of the insects that acts as a vector for the particular disease.
Thus, the correct answer is option (a).