单项选择题

This passage in general is about（）

A．Halley and other scientists
B．the orbit of a comet
C．Newton and Halley
D．Halley and his discovery

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单项选择题Halley made his discovery （）

A．by doing experiments
B．by means of his own careful observation
C．by using the work of other scientists
D．by chance

单项选择题When the baby was first sent to the hospital in London, her illness was considered to be （）

A．quite easy to treat
B．the result of thallium poisoning
C．a common one
D．extraordinarily serious