题干

下列有关动物细胞克隆和胚胎工程的叙述正确的是(   )


A:从个体中分离出单个组织进行培养是细胞克隆最基本要求

B:成纤维细胞间的胶原纤维可用纤维素酶水解

C:在人胚胎发育过程中只有受精卵具有全能性

D:选择胚胎干细胞作为核供体进行核移植可提高动物克隆的成功率

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D

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    You may have seen a talking parrot on a TV show, in a movie, or even in someone's home. The parrot has learned to copy sounds that people make. Birds are not the only animals that can copy the noises they hear. Dolphins, bats, and some apes also copy sounds. Now we can add elephants to this list of copycats.

    Dr. Joyce Poole is a zoologist. She studies the sounds of elephants. While she was in Kenya, she would hear strange noises made by Mlaika after sunset. Mlaika was a 10-year-old African elephant.

    Mlaika lived near a highway. Dr. Poole says, “I could not tell the difference between Mlaika's call and the distant truck noise.” She and other scientists studied Mlaika's sounds. It turned out that Mlaika was copying the sounds of the trucks driving by. Why would Mlaika copy trucks that she heard going by on the highway? Animals that are able to copy sounds may enjoy practicing new sounds. When they are kept outside of their natural environment, they may copy unusual sounds. That may be why an elephant would copy the sound of a truck.

    “Mlaika was not the only copycat elephant,” Dr. Poole says. Calimero is a 23-year-old male African elephant. He spent 18 years with two female Asian elephants. Asian elephants make chirping sounds (sounds made by birds) to talk with one another. African elephants usually do not make chirping sounds. But Calimero now does. He is copying his Asian elephant friends. Dr. Poole says that elephants need to form bonds with their family and friends. She says, “They make sounds to communicate with each other. When they are separated, they use sounds to keep in contact.”

    Parrots, dolphins, humans, and elephants show that being a copycat is one way that animals and people make new friends and keep old ones.