Final answer:
The Strait of Malacca and Singapore Strait are collectively known as the "world's busiest commercial waterway", due to their strategic importance in connecting the Indian Ocean with the Pacific Ocean through the South China Sea. The correct option is option A.
Step-by-step explanation:
The two straits that are collectively known as the "world's busiest commercial waterway" are Strait of Malacca and Singapore Strait. These straits are crucial maritime channels in Southeast Asia, linking major economies and facilitating a significant volume of global trade.
The Strait of Malacca, situated between the Malay Peninsula and the Indonesian island of Sumatra, is notoriously narrow and is the most direct maritime route from the Indian Ocean to the Pacific Ocean via the South China Sea. Just south, the Singapore Strait continues this path, connecting to the busy port of Singapore.
The collective importance of these waterways for international shipping, along with their historical and contemporary significance in global commerce, underscore their recognition as the busiest commercial waterway.