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in the world. (未知的 ) 2. Maths is short for ______________. unknown mathematics 3. English is _______ (wide) spoken all over the world. 4. They are famous for the ____________ (discover) of radium. 5. The boy wants to be a ___________ (science) when he grows up. widely discovery scientist Formal and informal language When we speak or write, we can use formal and informal language. We use formal language with our teachers or unfamiliar people. However, when we speak or write to our friends, we use informal language. our teachers, unfamiliar p