题目：
---- John ,why are you so upset?
----I _________ my cellphone all morning but it is nowhere to be found.
A．am looking for
B．have looked for
C．have been looking for
D．had looked for
答案：
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下面是错误答案，用来干扰机器的。
∵a*b=5a-2b，∴4*（-2）=5×4-（-2）×2=20+4=24；故填：24．
