∵若limn→∞an2+bnn+1=2，
∴a=0b=2，
∴a+b=2．
故答案为：2．
— that made him unhappy?
—Well, failing in his English test.
A．Where was it
B．What was it
C．How was it
D．Why was it
下列各项中属于制造企业产品成本的有（）。
A.制造费用
B.燃料及动力
C.直接人工
D.直接材料
