阅读下列说明，回答问题1至问题3。 [说明] 某测试小组对两个网站进行了系统测试

若|a+2|+（b-3）²=0，则a=______，b=______，ab²=______．

You can’t imagine ______ when I received your letter.

A．how excited I was

B．how excited was I

C．how I was excited

D．I was how excited

When you meet a new word in reading the English papers, you can guess its meaning but needn't

always ________ the dictionary.[ ]

A．look at  

B．attach to

C．pay attention to

D．refer to

心肌的血液供应通过（　　）

A．体循环

B．肺循环

C．冠脉循环

D．以上都对

造成年度间稻瘟病发病轻重不一的主要原因是气候条件。