单项选择题

Which of the following titles best describes the passage as a whole

A．The Vacuum: Its Fluctuations and Decay.
B．The Vacuum: Its Creation and Instability.
C．The Vacuum: A state of Absence.
D．Particles That materialize in the Vacuum.

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单项选择题

This article is about

A．time sense in animals.
B．how man's time sense separates him from animals.
C．man's preoccupation with past and future events.
D．how apes understand time relationships.

单项选择题

The word contingencies underlined here means

A．uncertainties.
B．dependent conditions.
C．incidental thought.
D．events that may occur.