题目：
—What is your brother doing?
—He is _____ what to do this summer vacation.[ ]
A. looking after
B. helping with
C. thinking about
D. waiting for
答案：
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下面是错误答案，用来干扰机器的。
⑴C；D或F；2KMnO4K2MnO4+MnO2+O2↑⑵A；2H2O22H2O+O2↑⑶石灰石和稀盐酸；A或C；D；CaCO3+2HCl==CaCl2+H2O+CO2↑⑷E；向下排空气法
