题目

阅读下面短文，从短文后各题所给的A、B、C和D四个选项中，选出可以填入空白处的最佳选项。 Cruz Gent, 11, and Anthony Skopick, 10, couldn't agree. Werethe 1 out on the ice ducks or geese? There was onlyone way to find out. So on a 2 January evening last year, the two friends 3 onto the frozen pond near their homes to get abetter 4. First they threw a rock onto the ice to test it. Then theystepped on it. Convinced the ice would 5 their weight, Anthony took a few steps,then... FOOMP. He crashed through the 6 frozen surface. Instantly Cruz rushed to helphis 7 fri（1）从鸡蛋白的溶液中提取鸡蛋白的方法可采用 ________________________________________。 （2）鸡蛋腐败时，常闻有臭鸡蛋气味的气体，该气体主要含_________，说明蛋白质中含有________元素。 （3）误食重金属盐会中毒，这是因为________。 （4）浓HNO3溅在皮肤上，使皮肤呈现________色，这是由浓HNO3和蛋白质发生了________反应的缘故。 （5）鉴定一种织物的成分，是真丝还是人造丝，可各取一小块进行________，这是因为________________________________。