Books are a worthy invention of human history since they make it possible for us to make a __ of human's thoughts.
Only when the government increases affordable homes for low-income groups______.
Not until________,_________.
It was in the factory _________ his friend worked _______ he picked up a lot of experience.
It is the film _______ director is Steven Spielberg _______ attracts quite a few viewers throughout the world.
——Where did you come across our chemistry teacher ? ------ It was in the supermarket ______ I purchased mooncakes. that B. which C. where D. when