We can never forget the days _______the two astronauts in spaceship worked together and the days _______we spent together.

I’ll never forget the day ________ we worked together

Lawrence Craven, a doctor from the USA, is the author of several published reports, one of ________ introduced the idea in 1953 _________ aspirin could reduce the risk of heart attacks.

I don’t know the reason _______ you were absent from the meeting, and I am not sure that someone will tell me the reason _______ you haven’t told me.

Here is my classmate ________ bicycle was lost yesterday.