This is a marginal sea that is part of the Pacific Ocean, and touches - among others - the countries of China, Vietnam, and the Philippines.

The question is asking for the name of that Sea - and it's the South China Sea.

The other countries facing this sea are Taiwan, Malaysia, Brunei and Singapore.

It's a "marginal sea" because it's part of the ocean, but it's partially separated from the main part of the ocean by islands.