各类营养物质在人体消化道内开始被消化的顺序是：（ ）
①蛋白质 ②淀粉 ③脂肪 ④无机盐．
A．①②③
B．①③④
C．②①③
D．③②①
淀粉的消化从口腔开始，口腔中的唾液淀粉酶能够将部分淀粉分解为麦芽糖，当淀粉和麦芽糖进入小肠后，由于小肠中的胰液和肠液中含有消化糖类的酶，因此，淀粉等糖类物质在小肠内被彻底消化为葡萄糖；蛋白质的消化是从胃开始的，当食物中的蛋白质进入胃以后，在胃液的作用下进行初步消化后进入小肠，小肠里的胰液和肠液含有消化蛋白质的酶，在这些酶的作用下，蛋白质被彻底消化为氨基酸；脂肪的消化开始于小肠，小肠内的胰液和肠液中含有消化脂肪的酶，同时，肝脏分泌的胆汁也进入小肠，脂肪在这些消化液的作用下被彻底分解为甘油和脂肪酸；无机盐不需要消化人体可以直接吸收．因此①蛋白质②淀粉③脂肪在人体消化道内开始被消化的顺序是：②①③．
故选：C
| At the beginning of the twentieth century, North American society held, as an ideal, the Nuclear Family. This presumably perfect residential, social, and economic unit consisted of an adult male, an adult female and their minor children. This structure was thought to be stable and long lasting. However, a few decades later, the structure of that ideal family was being altered radically even while it was being touted as the structure to be aimed for. Popular magazines bemoaned the loss of the Nuclear Family and its replacement with inferior forms. There are a number of factors that are acting in concert to apply pressure on the Nuclear Family and generate a variety of new structures. Some of these are: The definition of marriage has changed somewhat in that few people now consider it to last "until death do us part." The concept of monogamy (the marriage of one man and one woman) has been modified to a form now referred to as serial monogamy (the marriage of one man and one woman at a time). This reflects the increasing equality of women and men in terms of economic advantage and the recognition that many women no longer depend on men for their survival. Women are acquiring independence and have become empowered to make their own choices. With this independence, the need to form a relationship with a man becomes less important. This change embodies the concept that the marriage is temporary and can be terminated by either partner at any time. Associated with this, of course, is the relaxation of the divorce laws and the significant reduction of the shame that had one time been attached to divorce. The economy of North America has resulted in a two-tier system of a few rich who control most of the resources and a large portion of the population who control almost none of the resources. Because of this, many couples are forced to have both partners with full-time jobs outside the home. There are unintended byproducts of the need for a double income. The most important of these is the replacement of a mother-oriented socialization of children to a "stranger-oriented" socialization system reflected in the growth of the childcare industry. Also, either partner is financially able to end the marriage without significant hardship. The combination of these changes will in the coming decades have a profound effect on the structure of the family of North America. As a result, the family will be a fluid, constantly changing structure with variable household arrangements as the norm. |
In Paragraph 4, "until death do us part" probably means remaining married______.
A．until death
B．to the particular person until death
C．to one person at a time
D．until one leaves