单项选择题

Plateau's experiments were the first steps leading to the invention of ______.

A．eyeglasses
B．telescopes
C．bifocals
D．motion pictures
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单项选择题
A picture remains on the retina for ______.
A．6 seconds
B．second
C．16 seconds
D．1/6 of a second
单项选择题
The images that we see are recorded in ______.
A．the brain
B．the eye
C．the retina of eye
D．the pupil
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