整个教学工作的中心环节是（）。 A.备课 B.上课 C.课外辅导 D.成绩评定

患者，男性，83岁。原有冠心病病史3年余，因胸闷、胸痛2小时入院。查体：BP130／86mmHg，P78次／分，R20次／分，双肺未闻及干湿啰音，心脏听诊未闻及病理性杂音，双下肢无水肿。心肌酶谱升高，心电图示：V₁～V₄导联Q波形成，ST段抬高。

针对该心律失常最正确的治疗方法是（）

A.临时心脏起搏器

B.普罗帕酮慢推

C.同步电复律

D.非同步电复律

E.阿司匹林

1.5与0.5的差是多少？和是多少？

Ali is an antique dealer and one Saturday in November 2007 he put a vase in the window of his shop with a sign which stated ‘exceptional piece of 19th century pottery – on offer for €500’.Ben happened to notice the vase as he walked past the shop and thought he would like to have it. Unfortunately, as he was late for an important meeting, he could not go into the shop to buy it, but as soon as his meeting was finished he wrote to Ali agreeing to buy the vase for the stated price of €500. The letter was posted at 11:30 am.Later on the same day, Chet visited Ali’s shop and said he would like the vase but was only willing to pay €400 for it. Ali replied that he would accept €450 for the vase, but Chet insisted that he was only willing to pay €400 and left the shop. However, on his journey home Chet realised that €450 was actually a very good price for the vase and he immediately wrote to Ali agreeing to buy it for that price. His letter was posted at 12:30 pm.Just before closing time at 5 pm. Di came into Ali’s shop and she also offered €400 for the vase. This time Ali agreed to sell the vase at that price and Di promised to return the following Monday with the money.On the Monday morning Ali received both of the letters from Ben and Chet before Di could arrive to pay and collect the vase.Required:From the point of view of the law of contract advise Ali as to his legal relations with Ben, Chet and Di. (10 marks)

具有明显兴奋子宫作用的有效成分是（）

A．隐丹参酮 

B．川芎嗪 

C．延胡索乙素 

D．益母草碱 

E．红花黄色素

基坑土方开挖对降水有什么要求？