皮皮学，免费搜题
登录
搜题
【单选题】
已知(HF) 2 (g) 2HF(g) ΔH>0，且平衡体系的总质量(m 总 )与总物质的量(n 总 )之比在不同温度下随压强的变化曲线如图所示。下列说法正确的是A.
温度：T 1 2
B.
平衡常数：K(a)＝K(b)
C.
反应速率：v b >v a
D.
当 时，n(HF):n[(HF) 2 ]＝2:1
拍照语音搜题，微信中搜索"皮皮学"使用
参考答案：
参考解析：
知识点：
皮皮学刷刷变学霸
举一反三
【简答题】建筑安装工程计价可采用 和 计税。
【简答题】8051的堆栈区一般开辟在（）
【简答题】为庆祝九七回归祖国,四支足球队进行比赛,已知情况如下,问结论是否有效 ? 前提:( 1 )若 P 队得第一,则 Q 队或 R 队获亚军; ( 2 )若 R 队获亚军,则 P 队不能获冠军; ( 3 )若 S 队获亚军,则 Q 队不能获亚军; ( 4 ) P 队获第一; 结论:( 5 ) S 队不是亚军。
【单选题】关于建筑安装工程费用中建筑业增值税的计算，下列说法中正确的是（）
A.
当事人可以自主选择一般计税法或简易计税法
B.
一般计税和简易计税中的建筑业增值税税率相同
C.
采用简易计税法时，税前造价不包含增值税的进项税额
D.
采用一般计税法时，税前造价不包含增值税的进项税额
【多选题】How is fertilization carried out?
A.
Of the 300 million human sperm ejaculated during sexual intercourse, only about 200 reach the site of fertilization in the oviduct. Sperm are attracted to an ovulated egg by chemical signals released by both the egg and the supporting cells that surround it. Once a sperm finds the egg, it must migrate through a protective layer of cells and then bind to, and tunnel through, the egg coat, called the zona pellucida.
B.
Finally, the sperm must bind to and fuse with the underlying egg plasma membrane. Although fertilization normally occurs by this process of sperm–egg fusion, it can also be achieved artificially by injecting the sperm directly into the egg cytoplasm; this is often done in infertility clinics when there is a problem with natural sperm–egg fusion.
C.
Although many sperm may bind to an egg, only one normally fuses with the egg plasma membrane and introduces its DNA into the egg cytoplasm. The control of this step is especially important because it ensures that the fertilized egg—also called a zygote—will contain two, and only two, sets of chromosomes. Several mechanisms prevent multiple sperm from entering an egg. In one mechanism, the first successful sperm triggers the release of a wave of Ca 2+ ions in the egg cytoplasm. This flood of Ca 2+ in turn triggers the secretion of enzymes that cause a “hardening” of the zona pellucida, which prevents “runner up” sperm from penetrating the egg. The Ca 2+ wave also helps trigger the development of the egg. To watch a fertilization-induced calcium wave.
D.
The process of fertilization is not complete, however, until the two haploid nuclei (called pronuclei) come together and combine their chromosomes into a single diploid nucleus. Soon after the pronuclei fuse, the diploid cell begins to divide, forming a ball of cells that—through repeated rounds of cell division and differentiation—will give rise to an embryo and, eventually, an adult organism. Fertilization marks the beginning of one of the most remarkable phenomena in all of biology—the process by which a single-celled zygote initiates the developmental program that directs the formation of a new individual.
相关题目：