单项选择题

The word "this" in Line 4, Para. I refers to ______.

A．the results of recent research
B．dangers inherent in the nature of weeds
C．risks of altering crops' genetic make-ups
D．threats posed by chemicals used to kill weeds

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热门试题

单项选择题

The author suggests that the main impact that gene transfer between crops and weeds could have is ______.

A．the collapse of the agricultural industry
B．the rapid development of unintended plant hybrids
C．the development of pest and herbicide-resistant weeds
D．the difficulty to determine whether to make crops resistant to pests or not given the limited nature of current research

单项选择题

According to the passage, genetic engineering can be used to ______.

A．make crops hardier
B．kill weeds through cross-breeding
C．make crops resistant to chemical fertilizers
D．improve the yield and quality of most crops