Science and technology is changing fast nowadays. I bought this MP3 player at the beginning of this year but now it's out of________.
By the time he was ten, Edison _________ experiments in chemistry.
The businessperson wanted to sell his goods fast; ______, he chose his partner with great care.
Do you know the man____ is talking with Tom?
A dictionary is a book ______ gives the meanings of words.
The old town has narrow streets and small houses ________ are built close to each other.