The correct answer is option 4, Trading.

To understand why trading is considered a tertiary activity, let`s first understand what tertiary activities are. Tertiary activities refer to those economic activities that involve the provision of services rather than producing goods. In other words, they are activities that do not involve direct production or extraction of raw materials.

Option 1, Farming, and option 2, Weaving, are examples of primary and secondary activities, respectively. Farming involves the cultivation of crops and rearing animals, which is a primary activity. Weaving involves the production of fabric from raw materials like cotton or wool, which is a secondary activity.

Option 3, Manufacturing, is also a secondary activity as it involves the transformation of raw materials into finished goods.

Option 4, Trading, falls under the category of tertiary activities. Trading involves the buying and selling of goods or services between different entities. It is a service-based activity that facilitates the exchange of goods and services between producers and consumers.

In summary, while farming, weaving, and manufacturing are primary and secondary activities, trading is a tertiary activity.