Tijuana and Mexicali: (A) are planning to participate in the maquiladora program. (B) are located just opposite the U. S. city of El Paso. (C) were among the first border cites to experience a growth surge. (D) are key cities in the south of Mexico.

C) were among the first border cites to experience a growth surge.

Explanation:

During the 1960's, maquiladora industries quickly grew geographically and economically and by 1985, had become Mexico's second largest source of income from exports, after income accounted to oil. After 1972, maquiladoras have also been half of Mexico's exports.

Tijuana became a dominant city in the border between California and Mexico, with a notable economic and industrial grow across the north of Mexico. Bordering San Diego, CA, Tijuana has around 600 industrial complexs that range from electronics, consumer, aerospace and medical industries. Tijuana holds the largest medical device manufacturing in all of the continent. Aerospace devices are also a motor for the region.

The rapid growth lead to heavy waves of working migrants moving there.

Similarly, Mexicali has greatly grew into a manufacturing hub, along tourism trade and the constructing sector. The Mexicalli Valley is becoming

a center that attracts more investment and makes relying more to the neighbouring Mexico.