I've just come back from a holiday in the United States
我刚从美国度假回来。
May I ask where you come from?
请问贵处。
I am always tired when I come home from work.
我下班回家时总是很疲倦。
I come from China, a beautiful city!
我来自中国，一个美丽的.城市！
I come from a world full of life!
来自充满鲜活生命的世界！