慢性阻塞性肺气肿出现哪些症状和体征（）
A.扁平胸
B.呼气性呼吸困难
C.混合性呼吸困难
D.胸部X线片大致正常
E.桶状胸
参考答案：B, E
若（1-2x）2010=a0+a1x+a2x2+…+a2010x2010（x∈R），则（a0+a1）+（a0+a2）+…+（a0+a2010）=______（用数字回答）
The ______ Approach is a grammar-based method in which principles of grammatical and lexical gradation are used and new teaching points presented and practised through meaningful situation activities.
