题干

下列对细胞分化时期的叙述,最确切的是(   )

A:只发生在胚胎发育的早期

B:发生在细胞分裂过程中

C:发生在生物体的整个生命进程中

D:发生在胚胎发育的整个过程中

上一题 下一题 0.0难度 选择题 更新时间:2018-03-03 06:02:05

答案(点此获取答案解析)

C

同类题3

阅读理解

    New York Time—A gunman killed eight people at a mall in Omaha this afternoon and then killed himself, setting off panic among holiday shoppers, the police said.

    "The person who we believe to be the shooter has died from self-inflicted gunshot wounds," Sergeant Teresa Negron of the Omaha Police Department said at televised news." We have been able to clear the mall," she said." We don't believe we have any other shooters." The police said that at least five other people had been injured in the shootings.

    She did not give the shooter's identity." We are still conducting the investigation," Sergeant Negron said, adding that the city's mayor, who was out of town, was on his way back to Omaha.

    She said the police received a 911 call from someone inside the Westroads Mall on the west side of Omaha, and shots could be heard in the background. The first police officers arrived at the mall six minutes after the first call, she said but by then the shootings were over.

    It is reported that the gunman left a suicide note that was found at his home by relatives. A law enforcement official who spoke on condition of anonymity(匿名)said the note indicated that the gunman wanted to "go out in style."

    The shootings broke the usually ordinary routine of holiday shopping. The gunman was said by some witnesses to have fired about 20 shots into a crowd. Some customers and workers ran screaming from the mall, while others dived into dressing rooms to hide from the shooter.

    Shoppers and store workers were trapped inside the mall, which has roughly 135 stores. Others streamed out of mall exits with their hands raised. President Bush was in Omaha this morning to deliver a speech, but he had left the city by the time the shootings took place.

根据短文内容,请将单词填写在题号对应的横线上。

同类题4

完形填空

    “Who can ever have imagined someone like me would make it this far?” asked Chad Wood last week during his high school graduation speech as the best student. Chad offered1to his fellow classmates to never give up---and the words2much more to himself. That's because Chad is deaf, and he told the story of the serious troubles he3to graduate first in his class at Harrison High school in Kennesaw, Georgia.

    Chad didn't start to4until he was 5, according to his mother, Pam Wood. Although her son was5a disadvantage, she was determined not to treat him6. “I've expected him to do everything every other kid does, and I saw no7why he couldn't,” she told ABC News. “And if he8the first time, we just tried again.”

    Chad, 17, worked hard throughout school,9no special treatment but sitting at the front of the class and using a special audio system so he could hear the teacher. All his hard work10. He received full school fare to Vanderbilt University. “Deafness had taught me a lesson to never11,” he said in the speech. “Not when the experts tell you it cannot be done. Not when you have12so far behind that escaping seems the only way 13. Not when achieving your dreams seems an entire14.”

    Chad spoke for about four minutes, after which he received a standing applause from the class and15messages from family, friends and strangers. “They've been sending me messages on Facebook, email, they've been talking to me in person telling me how it had a16on their lives and how they're really17by it,” Chad told ABC News. “It feels18. Seeing that my words19have a power on someone and that they want to work harder because of my words makes me feel20.”