单项选择题

The crown of the tooth is covered by a layer of ____, the hardest substance in the body.
A、enamel
B、dentin
C、pulp cavity
D、 root canal

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不定项选择

In accordance with IAS 37 Provisions, Contingent Liabilities and Contingent Assets whether the following item would require a provision in the financial statements?
A compensation claim against the company by an employee which the legal advisors believe the employee is likely to win.

A．错误
B．正确

单项选择题

一往复活塞式压缩机工作压力为15MPa，它属于（）压缩机。
A、高压
B、中压
C、低压
D、超高压