Explanation:

In hot summer and cold winter, the number of malaria cases as well as Anopheles mosquitoes decline. This is because the life cycle of the malaria parasite (Plasmodium) is dependent on both the human host and the Anopheles mosquito.

During hot summer and cold winter, the conditions are not suitable for the survival and reproduction of Anopheles mosquitoes. The cold temperatures in winter and high temperatures in summer can negatively impact the survival and breeding of mosquitoes. Additionally, the hot and dry conditions during summer can lead to a decrease in the availability of water bodies required for mosquito breeding.

However, the reoccurrence of malaria in humid warm conditions is due to the presence of mosquito larvae in permanent waters. Here is the explanation for this:

Surviving Malarial Parasites in Human Carriers:
- Malaria is transmitted to humans through the bite of infected female Anopheles mosquitoes.
- When a mosquito bites an infected person, it ingests the gametocytes (sexual stage of the parasite) along with the blood.
- Inside the mosquito, the gametocytes mature and undergo sexual reproduction, resulting in the formation of sporozoites.
- The sporozoites then migrate to the salivary glands of the mosquito, ready to be transmitted to another human host during a subsequent blood meal.
- However, during hot summer and cold winter, the number of infected mosquitoes declines, reducing the chances of transmission to new human hosts.

Surviving Sporozoites in Surviving Mosquitoes:
- In addition to the decline in infected mosquitoes, the survival of the sporozoites within the mosquitoes is also affected by extreme temperatures.
- Cold winter temperatures can kill or reduce the survival rate of the sporozoites within the mosquitoes.
- Similarly, high temperatures during summer can also negatively impact the survival and infectivity of the sporozoites.
- As a result, the number of surviving sporozoites in the surviving mosquitoes decreases, further reducing the chances of malaria transmission.

Monkeys:
- While some species of monkeys can serve as reservoir hosts for malaria parasites, their role in the reoccurrence of malaria in humans during humid warm conditions is not significant.
- The primary mode of transmission for human malaria is through the bite of infected Anopheles mosquitoes, and monkeys are not the primary hosts for human malaria parasites.

Mosquito Larvae in Permanent Waters:
- The primary reason for the reoccurrence of malaria in humid warm conditions is the presence of mosquito larvae in permanent waters.
- Permanent water bodies, such as stagnant ponds, lakes, or puddles, provide suitable breeding grounds for mosquitoes.
- When there is an abundance of permanent water sources, it creates the ideal conditions for mosquito breeding and population growth.
- As the mosquito population increases, so does the risk of malaria transmission to humans.

Therefore, the correct answer is option 'D' - Mosquito larvae in permanent waters. The presence of mosquito larvae in permanent waters during humid warm conditions leads to an increase in the mosquito population, consequently increasing the chances of malaria transmission to humans.