A pencil has teeth marks on it.
A. The person who used the pencil was nervous.
B. The pencil was chewed up by a toddler or pet.
C. Someone or something chewed the pencil.
D. The pencil belongs to someone who is trying to quit smoking.
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People are crowding around the entrance to a toy store, which won’t open for another hour.
A. The store is the only toy store in the entire state.
B. There is always a crowd like this an hour before opining.
C. The store has paid a crowd to show up.
D. The store is having a well-publicized sale.
Inside a car with an out-of-state license are several maps, suitcases, and bags of snacks.
A. The driver of the car is on vacation.
B. The driver of the car is on a business trip.
C. The driver of the car has children.
D. The driver of the car is on a trip of some kind.
化学反应焓变的测定实验中为什么把0.200 mol·L－1 CuSO4溶液用移液管准确吸取，而锌粉用台秤称量？
本实验对所用量热器应有什么要求？是否允许有残留水滴？是否需要用CuSO4溶液润洗？为什么？
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