第11题: [单项选择]After children have helped to set the table with impressive accuracy, they________. A. are able to help parents serve dishes B. seat themselves and wait for their meals C. are able to figure out the total pieces D. can enter a second-grade mathematics class 参考答案:C 答案解析:本题是一道细节题。在本文第一段中“Soon they are capable of noting that they have placed five knives, five spoons, a
第16题: [单项选择]正常共同凝血途径中,以下哪项是正确的() A. 因子Ⅸa,Ⅷa,PF33,Ca2+形成复合物 B. 因子Ⅲ,Ⅶa,Ca2+形成复合物 C. 因子Ⅹa,Ⅴa,PF3,Ca2+形成复合物 D. 因子Ⅸ,Ⅷ,Ⅱ,磷脂,Ca2+形成复合物 E. 因子Ⅻa,Ⅸa,PF3,Ca2+形成复合物 参考答案:C
第17题: [单项选择]下列黄酮类化合物酸性强弱顺序正确的是() A. 7-羟基黄酮>6-羟基黄酮>5-羟基黄酮 B. 7-羟基黄酮>5-羟基黄酮>6-羟基黄酮 C. 6-羟基黄酮>7-羟基黄酮>5-羟基黄酮 D. 6-羟基黄酮>5-羟基黄酮>7-羟基黄酮 E. 5-羟基黄酮>6-羟基黄酮>7-羟基黄酮 参考答案:A 答案解析:7-或4′-羟基酸性最强,5-羟基会与4-羰基形成分子内氢键,使此酚羟基不易电离出氢质子,所以酸性最弱。