问题
不定项选择题
将一定量的镁和铝，分别投入体积相同、物质的量浓度也相同的等质量的盐酸中。盐酸是分别放在天平的左右托盘上的两个相同的烧杯里的，加入镁和铝之前已经调整至平衡。要使反应完全后，天平仍保持平衡，则投入的镁和铝的质量的关系可能是 [ ]
A.m(Mg)>m(Al)
B.m(Mg)=m(Al)
C.m(Mg)<m(Al)
D.都可以
答案
BC
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将一定量的镁和铝，分别投入体积相同、物质的量浓度也相同的等质量的盐酸中。盐酸是分别放在天平的左右托盘上的两个相同的烧杯里的，加入镁和铝之前已经调整至平衡。要使反应完全后，天平仍保持平衡，则投入的镁和铝的质量的关系可能是 [ ]
A.m(Mg)>m(Al)
B.m(Mg)=m(Al)
C.m(Mg)<m(Al)
D.都可以
BC
| Modem cowboy seem to be giving up the bandanna (印花大手帕) handkerchief; yet there was a time when this article was almost as necessary to a cowboy’s equipment as a rope, and it served for purposes almost as varied. The bandanna made a good sling for a broken arm; it made a good bandage for a blood wound. Early Irish settlers on the Nueces River used to believe that a bandanna handkerchief that had been worn by a drowned man would, if cast into a stream above the sunken body, float until it came over the body and then sink, thus locating the body. Many a cowboy out on the lonely plains has been buried with a clean bandanna spread over his face to keep the dirt, or the coarse blanket on which the dirt was poured, from touching him. The bandanna has been used to hang men. Rustlers used to "wave" strangers around with it as a warning against nearer approach, though the hat was more commonly used for signaling. Like the Mexican sombrero (阔边帽) or the fourgallon Stetson, the bandanna could not be made too large. When the cowboys of the Old West make their final parade on the grassy shores of Paradise, the guidon (旗手) that leads them should be a bandanna handkerchief. It deserves to be called the "flag of the range country". |
The purpose of Paragraph 2 is to ______.
A．explain the burial rites of cowboys
B．protest the passing of the bandanna
C．compare the bandanna with the Stetson
D．show the varied uses of the bandanna