What do the xiongnu the uighurs the khitan and the jurchen have in common?

The xiongnu, the uighurs, the khitan, and the jurchen were all able to gain large amounts of valuable goods from China, often as disguised "protection money" that kept them from attacking China, and they all established nomadic empires to the north of China.

three to four minutes

Explanation:

They can suffocate and die quickly without water (following three to four minutes of no gill movement), so it's important that you don't take them out unless the new water is ready for their transfer.