单项选择题

According to the passage, dogs and cats ______ .

A．as well as human beings cannot see some colours
B．have fewer cones than human beings
C．have less rods than human beings
D．can see colours as well as human beings

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热门试题

单项选择题

When millions of rods in oar eyes are at work in darkness we can see ______ .

A．colours only
B．shapes and colours
C．shapes only
D．darkness only

单项选择题

Which of the following is NOT true about insects

A．Insects can see more colours than human beings.
B．Insects can see ultraviolet rays which are invisible to men.
C．All insects have their favorite colours.
D．The world is more colorful to insects than to human beings.