单项选择题

Pure science, leading to the construction of a microscope, ______.

A．is not always as pure as we suppose
B．may lead to anti-scientific, "impure" results
C．necessarily results from applied science and the discovery of a cell
D．necessarily precedes applied science, leading to the discovery of the cell
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单项选择题
We learn from the first paragraph that ______.
A．too much publicity can harm the chances for the success of a new food innovation
B．innovations that produce culturally acceptable crops will generally be successful
C．a food-product innovation can be technically feasible and still not be economically feasible
D．it is difficult to decide whether a food-product innovation has actually been a success
单项选择题
It can be inferred from the passage that the author assesses the truth about opaque-2-maize in that ______.
A．it is a more recent innovation that the use of fish-protein concentrates
B．it can be stored as easily as other varieties of maize
C．it is more popular than the fish-protein concentrates
D．it may be more susceptible to insects than other varieties of maize
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