急性心肌梗死早期，特别是入院前主要的死因最多见（）.
A.传导阻滞
B.室早
C.室颤
D.房早
E.房颤
参考答案：C
管理和销售费用预测包括______。
A．销售费用
B．销售费用占销售收入的比例
C．新市场的拓展
D．每年的研究和开发费用占销售收入的比例
–Why has Tom looked unhappy recently?
–He has some difficulty ______ with his new classmates at school.
A．getting over
B．getting in
C．getting along
D．getting down
