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单项选择题

Which of the following statements is true of fraternal twins

A．They have the same blood type.
B．They can be of different sexes.
C．They have the same genes.
D．They occur at random in the population.
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热门试题

单项选择题The passage seems to concentrate on ______.

A．how twins are born
B．how twins grow up
C．characteristics of identical twins
D．ways to distinguish twins

单项选择题What does the man mean to illustrate through the example

A．Badly-educated people are careless in their speech.
B．The English language is being degraded.
C．Well-educated people are more likely to err.
D．Well-educated people are going to the dogs.