What was done to protect the Chinese empire against Invaders? O they attacked the enemies first
O built the Great Wall
Omore soldiers were drafted
O installed fortifications on the rivers

They built the Great Wall

Explanation:

The Ming dynasty built a giant wall stretching 5,000 miles to keep invaders out of China, but how effective was it against the enemy? The Great Wall is nearly 30 feet high along some stretches, and often built through rugged and mountainous terrain, such as the Huanghuacheng region near Beijing.