单项选择题

Giraffes do not have swollen legs because______.

A．their legs and feet have strong skin and muscles
B．their blood vessels are stiff and tough legs
C．they wear a kind of special suit
D．there are lots of one-way valves in the veins of their legs

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热门试题

单项选择题

According to the passage, the initial concern about computers was that they might______.

A．change our personal lives
B．take control of the world
C．create unforeseen problems
D．affect our businesses

单项选择题

The passage is mainly about______.

A．what physical features the giraffe has
B．how the giraffe's heart works
C．how the giraffes heart pumps blood to its head
D．how the giraffes can stand up to high blood pressure