Courtesy costs nothing. Lower the toilet seat after use. Let the people in the elevator exit before you enter. Return shopping carts to their designated areas. When you borrow something, return it better shape (filled up, cleaned) than when you got it.
哭着送去,哭着回来,回来后要努力于衣食之物的生产,资助祭祀,并用来孝顺双亲。 
Urban forestry proves that nature and cities can thrive together.
The power to edit genes comes with great ethical obligations.