A long time ago, there was a man. He wa nted to buy a pair of new shoes. He measured(量) his feet with a straw(稻草)，and then went to a shoe shop in town.

    The shopkeeper took out a pair of new shoes, and let him try it on. But when he looked into his pocket, he found that the straw was not there. So he said, “I'm sorry, I forgot to bring the size(尺寸) here! Let me go home to get it.” After that, he ran out of the shop. It was very far from his home to the shoe shop. When he got back home, he was out of breath.

    With a straw in his hand, he hurried to the shoe shop again. But the shop was closed.

    Someone near the man said, “Your feet are with you. Why don't you try which pair of shoes fits(合适)? And why do you believe your straw, but not your feet?”

如图，小俊在A处利用高为1.5米的测角仪AB测得楼EF顶部E的仰角为30°，然后前进12米到达C处，又测得楼顶E的仰角为60°，求楼EF的高度．（结果精确到0.1米）

能吞食大量细菌，对污水有一定净化作用的单细胞生物是（  ）

先化简，再求值：

2x²+3（﹣x²+3xy﹣y²）﹣（﹣x²﹣2y²），其中x= $\frac{1}{2}$ ，y=﹣2．

材料二：APEC发展模式是一种全新的国际合作方式。江泽民同志在1996年菲律宾苏比克会议上首次提出了“APEC方式”这一概念。在1995年大阪会议上，江泽民宣布了大幅度降低进口关税，到2005年将工业品平均关税降到了10%。在1997年温哥华会议上，江泽民建议APEC制定一项《走向21世界的科技产业合作议程》。该建议得到APEC成员一致赞同和支持。