单项选择题

What is NOT true about a theory

A．A useful theory can explain past observations.
B．A useful theory helps to make predictions.
C．A theory is the truth that does not need to be tested.
D．A theory may have to be revised or rejected some times.

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单项选择题

In Paragraph 5, the author refers to a hypothesis as a leap into the unknown in order to show that hypotheses ______.

A．go beyond available facts
B．are sometimes ill-conceived
C．can lead to dangerous results
D．require efforts to formulate

单项选择题

Science involves ______.

A．imagination and creative thinking
B．collecting information
C．performing experiments
D．all of the above