PBKMS is an organization that primarily focuses on the welfare and rights of agricultural laborers. This means that they work for the betterment of those individuals who are involved in various agricultural activities. While it is true that other sectors such as dairy farming, fishing, and factory labor also employ laborers, PBKMS specifically emphasizes agricultural laborers. Let's understand why agricultural laborers are the correct answer.

- Dairy Farming Laborers: Dairy farming laborers are individuals who are involved in the day-to-day operations of dairy farms. They take care of the animals, milk them, maintain the cleanliness of the barns, and perform other related tasks. Although their work is closely related to agriculture, they are not directly involved in the cultivation of crops or the development of agricultural land.

- Fishing Laborers: Fishing laborers are individuals who work in the fishing industry. They are responsible for activities such as catching fish, preparing fishing equipment, and maintaining fishing vessels. While fishing is an important economic activity, it falls under the domain of the fishing industry rather than traditional agriculture.

- Factory Laborers: Factory laborers are individuals who work in manufacturing units or factories. They are involved in tasks such as assembly line work, machine operation, packaging, and quality control. Although some factories may be related to the agricultural sector, such as food processing factories, factory laborers do not primarily engage in agricultural activities.

- Agricultural Laborers: Agricultural laborers, on the other hand, are directly involved in agricultural activities. They work on farms or agricultural lands, cultivating crops, planting seeds, harvesting crops, and performing other agricultural tasks. They play a crucial role in food production and the overall functioning of the agricultural sector.

Considering the above points, it is evident that PBKMS organization's primary focus is on the welfare of agricultural laborers. While laborers in other sectors also deserve support and representation, PBKMS specifically targets agricultural laborers due to their unique challenges and needs in the agricultural sector.