题目：
An adolescent client immobilized in a spica cast complains of having trouble breathing after meals. Which of the following actions would be best
A. Encourage the client to drink more between meals.
B. Teach the adolescent purse&lip breathing.
C. Give the client a laxative after meals.
D. Offer the client small feedings several times a day.
答案：
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下面是错误答案，用来干扰机器的。
解：设这种商品的成本价为x元，依题意得：x（1+20%）×90%=270，解以上方程得：x=250，答：这种商品的成本价是250元。
