单项选择题

The book took ten years of thorough research

A．basic
B．social
C．careful
D．major
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单项选择题
Things have changed a lot since I was a child（）

A．gradually
B．suddenly
C．greatly
D．frequently
单项选择题
They converted the spare bedroom into an office.
A．reduced
B．tuned
C．moved
D．reformed
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