题干

下图表示某高等动物细胞的一个细胞周期中,每条染色体上的DNA含量变化曲线。错误的说法是(   )

A:AB段处于细胞分裂的间期

B:BC段细胞中存在姐妹染色单体

C:CD段表示分裂期的后期

D:纵坐标中N=1或2

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答案(点此获取答案解析)

D

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    Can you imagine printing food? Some scientists are trying to revolutionize the dining experience by doing this. They hope that having a 3D printer in the kitchen will become as commonplace as the microwave. Scientists say that they are easy to use:you simply have to select a recipe and put the raw food "inks" into the printer. You can also change the instructions to make the food exactly how you want it. This means that it would be very quick and easy to create tasty and nutritious meals.

    They say that if people used 3D printers to create meals there would be less need for traditional growing, transporting and packaging processes as food production would be a lot easier. For example, alternative ingredients (原料) such as proteins from insects could be changed into tasty products. And as is known,those traditional activities are not beneficial to our surroundings.

    This technology could also help people who suffer from dysphagia (a swallowing disorder).The patients could program the printer and softer versions would be made so that they would not have trouble swallowing them.

    However,some people think that using 3D-printed foods would be a disaster. It could take away many jobs,including those for growing,transporting and packaging food. Imagine a world where there was no need for farming or growing crops and the same tastes could be printed from a raw "food ink". Likewise, traditional cafes and restaurants might lose business. Also, there are concerns about the nutritional value of printed food:is it really possible to get the nutrients we need from food-based inks?

    What's more, cooking and eating together with family and friends has long been a traditional and enjoyable activity. It is hard to imagine a world where the pastime of cooking is dead and meals can be created at the touch of a button.