Answer: South China Sea
Step-by-step explanation:
The South China Sea has become a hotspot for contention amongst many countries in the region such as Vietnam, Philippines, China, Taiwan and Indonesia with all of them claimed sovereignty of sections of the sea that tend to overlap with one another.
China has been trying to exert it's dominance over this sea by increasingly being Aggressive and maintaining a strong naval presence there. Indeed just yesterday being May Day 2020, the Chinese Navy claimed to have expelled a USS Navy Destroyer from a section of the sea.
The sea is of strategic importance with over $3 trillion in trade and is said to be rich in oil.
With the sea being close to China's borders and with the US being allied to the Philippines, China would want to set this sea up as a buffer zone to protect it's borders from perceived US incursions as well.