题目

下列关于细胞的分化、全能性、衰老、凋亡和癌变叙述，正确的有（ ） ①细胞的分化、衰老和癌变对于生物体都是有积极意义的 ②细胞分化使多细胞生物中的细胞功能趋向全面化，提高细胞代谢的效率 ③人胚胎发育过程中尾的消失是细胞坏死的结果 ④细胞衰老表现为细胞核体积变小、色素含量增加、细胞膜的通透性降低 ⑤细胞凋亡受遗传物质的严格控制，并且在凋亡的过程中存在基因表达 ⑥细胞癌变主要是因为原癌基因和抑癌基因发生突变 ⑦癌根据材料内容选择最佳答案。Mr and Mrs Smith like China very much and they are in China with their children.Mr Smith is 40 years old. He is a doctor at a big hospital in Beijing, China now. His wife, Mrs Smith is 35 years old. She is an English teacher in an international (国际的) school in Beijing. Their son, Mike, is ten years old now. He is a student at his mother's school. They like their school very much. Their daughter, Mary, is only one year old. It's cold today, so Mary is at home.（1）How old is Mr Smith?A.30.B.35C.40.D.45（2）文中下划线单词的汉语意思是""A.妻子B.姐姐C.表姐D.姑姑（3）Mrs Smith is a.A.doctorB.teacherC.nurseD.manager（4）Mike isyears old.A.7B.8C.9D.10（5）It's a day today.A.warmB.coldC.coolD.hot