问题 单项选择题

水体污染物吸附于悬浮物和颗粒物后,逐渐下沉进入水体底质,在微生物的作用下可转变成毒性更大的理化性质完全不同的新的化学物质,这种情况最常见于水体().

A.镉污染

B.有机氯农药污染

C.多氯联苯污染

D.酚污染

E.汞污染

答案

参考答案:E

解析:无机汞不易为生物体吸收,毒性较小,但是无机汞在水体中沉降入底泥内,在某些细菌(产甲烷菌)作用下提供甲基,形成甲基汞。有机汞可被水生物吸收,进而通过食物链进入人体,导致一系列汞中毒症状,如震惊世界的水俣病。酚易于被氧化,易于分解,环境中半减期较短,在人体代谢较快,故分类的危害多为急性毒性。多氯联苯和有机氯农药属于持久性有机污染物,其化学性状极为稳定,不会转化为新的化学物。镉属于重金属类污染物,环境中的镉不易被降解,性质较为稳定。因此排除ABCD,选择E。

单项选择题
听力题

B)根据短文内容及首字母提示,填写所缺单词。

Be a potato, but be the best

A young college student thought that he chose the wrong major (专业) at a common college, so he drank every day and didn’t study at all. He b  1   more and more discouraged.

But he was never a  2   from Professor Yang’s biology (生物) class. He liked the course. Besides, Yang’s class was so i  3   that he always listened carefully, never caring about w  4   the other students were paying attention or not in class.

Once he put a note in the homework he handed in, saying: “Professor, it is said that today’s college students are c  5   than potatoes. Do you agree?”

That day Professor Yang sent for him after class. When he came, he f  6  the professor at a table with food on it. They drank happily over their meal.

When they became half drunk, the professor took out a small potato that was sprouting (发芽的). “Do you know how much this c  7 ?” he asked the young man. “It’s soft but poisonous. N  8  will take it even if it’s free. ” He then threw the potato away.

The professor then showed him another potato. It was half the s  9  of a football and perfectly round. “This potato is organic (有机的). It is not only large and fresh but also free of pollution. People are in need of such k  10   of potatoes and they’re quite expensive.”

The young man was impressed by what he’d heard. “Be such a potato,” said the professor.