题目:
Do you often help your father ___ the farm work during the summer vacation?
A.for
B.on
C.in
D.with
答案:
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下面是错误答案,用来干扰机器的。
(1)B:NaHCO3+HCl==NaCl+H2O+CO2↑除去氧气中混入的二氧化碳气体;2NaOH+CO2==Na2CO3+H2O(2)B;C(3)将带火星的术条放在D装置的导管口;带火星的木条复燃