当学习任务比较简单时，要求学习效益达到最佳水平，则合适的学习动机强度应当()A.很高

可以用于制备病毒灭活疫苗的化学药品是

A．甲醇

B．甲醛

C．乙醛

D．乙醇

E．乙酸

10 members were assigned in advance to your project team. This pre-assignment could because of all the following reasons EXCEPT:

A．People were promised as part of a competitive proposa

B．Suitable people came forward and mentioned that they wanted to work on the projec

C．Staff assignments were defined in the project charte

D．Project is dependent on the expertise of some of the pre-assigned person

城市用地共分为（）大类。

A.8

B.10

C.16

D.46

—Some Chinese students find it hard to adapt to the life when in London.

—Exactly, ______ they've learnt a lot about the city before.[ ]

A. if only      

B. now that    

C. as though      

D. even though

下列化学方程式符合题意且书写正确的是[ ]

A.铁和稀盐酸反应：2Fe+6HCl==2FeCl₃+3H₂↑

B.用稀硫酸洗去附着在试管壁上的铜：Cu+H₂SO₄==CuSO₄+H₂↑

C.实验室检验CO₂的方法：CO₂+Ca(OH)₂==CaCO₃↓+H₂O

D.除去NaOH中少量的Na₂CO₃：Na₂CO₃+2HCl==2NaCl+H₂O+CO₂↑