Which of the following is the best reason for pouring a condensation impression material as soon as possible()
A. the degree of polymerization of condensation polymers is initially high and then decreases with time
B. evaporation of a volatile by-product causes shrinkage ofthe set material
C. If left unpoured，condensation impression materials expand as they absorb water from air
D. condensation polymers will start to react with the polymer of the impression tray and cause distortion
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冷轧厂1780机组酸洗一段共设有()台热交换器，二段共设有()台热交换器，三段共设有()台热交换器，传热材料为()。
Dr Wang requested that you mix alginate and take an impression．While measuring the water，you got involved in conversation and did not notice how warm ir was．This oversight will()
A. make the mix unstable
B. 1engthen the gelation time
C. not affect gelation time
D. shorten the gelation time
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