单项选择题

The main idea of this passage is that ______.

A．nitinol is a highly versatile metal
B．nitinol helped make the space program a success
C．nitinol has revolutionized dental care
D．most alloys have "memories"

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单项选择题

Which of the following is NOT a step in forming nitinol for space use

A．The metal is shaped into ingots.
B．The metal is separated into nickel and titanium.
C．The metal is drawn into a wire.
D．The metal is set in its desired curve or shape and heated briefly.

单项选择题

We can conclude from this passage that ______.

A．nitinol has its "memory" function because it is an alloy
B．the sun's rays are necessary to trigger the metal's "memory"
C．people have only begun to discover the many uses of nitinol
D．one problem with nitinol is that it often returns to its original shape at inopportune time