单项选择题

By the concrete being too "green", the author means that the concrete has

A．become cracked.
B．not yet cured.
C．not dried out.
D．not settled in plac
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单项选择题
In mixing concrete, one of the desires the amateur must resist is to ______.
A．break off a corner to see if the "green" has gone
B．leave the form on too long
C．strip off the forms a day after the concrete has properly hardened
D．use too much water
单项选择题
The private postal services of the nineteenth century claimed that they could do which of the following better than the government
A．Deliver a higher volume of mail.
B．Deliver mail more cheaply.
C．Deliver mail faster.
D．Deliver mail to rural areas.
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