The correct answer is option 2: Petro-chemical. The Sun Belt of the U.S.A refers to the southern region of the country including states such as Florida, Georgia, Texas, and California. This region is important for the petro-chemical industry due to several factors. Firstly, the Sun Belt has abundant reserves of natural resources like oil and natural gas, which are essential raw materials for the petro-chemical industry. Additionally, this region has a favorable climate with plenty of sunshine, which is important for certain production processes in the petro-chemical industry. The proximity to major ports and transportation networks also makes the Sun Belt an ideal location for the industry. While the other industries listed in the options may also have presence in the Sun Belt, option 2 specifically highlights the significance of this region for the petro-chemical industry.