题干

某炭疽杆菌的A基因含有A1~A6 6个小段,某生物学家分离出此细菌A基因的2个缺失突变株:K(缺失A2、A3)、L(缺失A3、A4、A5、A6)。将一未知的点突变株X与L共同培养,可以得到转化出来的野生型细菌(即:6个小段都不是突变型);若将X与K共同培养,得到转化的细菌都为非野生型。由此可判断X的点突变最可能位于A基因的(   )

A:A2小段

B:A3小段

C:A4小段

D:A5小段

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A

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    Recently actor Adrien Grenier has launched(发动)a campaign to reduce the amount of single-use plastic usage in order to protect and save marine (海洋的)wildlife and the environment. Plastic drinking straws are among many single-use plastic products contributing to the great loss of marine life, but they're a great place to start because they're something that are used by millions of Americans who are unaware that they're so damaging.

    Americans use more than 500 million straws daily, which is enough to fill 127 school buses each day and they can't be recycled. That means plastic straws might end up in oceans, where fish and other marine wildlife mistake the small bits for food and swallow them. After seeing a photo of a beached whale with a belly full of plastic, Grenier felt the inspiration to launch the Lonely Whale Foundation, hoping to inspire and educate others on the challenges faced by marine wildlife.

    Along with stopping the use of straws, Grenier hopes to educate consumer on the dangers of other single-use plastic items such as grocery bags and water bottles. While many Americans use these plastic products in their daily life, there are many alternatives that can help protect the environment such as straws made from stainless steel, glass, and even bamboo instead of plastic.

    In addition to quitting your straw habit, you can further help the environment by taking the I Choose to Reuse commitment, and stop your use of single-use coffee cups, checkout bags and bottled water. Instead, take advantage of any number of alternative reusable products.

    Need another reason to stop drinking from straws? Grenier also says using straws can cause wrinkles!