单项选择题

What is the purpose of this class discussion

A．To discuss the results of the lab experiment.
B．To answer Bob’s question about the lab experiment.
C．To explain the method of collection by water displacement.
D．To prepare the students to do the lab experiment.

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单项选择题

What was deposited on the bottom of the gas bottle

A．Magnesium.
B．Limestone.
C．Carbon.
D．Water.

单项选择题

What caused the deposits

A．The hydrochloric acid broke the carbon bonds in tile carbon dioxide,
B．The magnesium oxide broke the carbon oxygen bonds in the carbon dioxide.
C．The burning magnesium broke the carbon oxygen bonds in the carbon dioxide.
D．The gas collection method broke the carbon-oxygen bonds in the carbon dioxide.