For a healthy life, windows and doors should be wide and usually they should () for at least 15 hours a day.

科目名称：理工英语3

试卷号：11377

题型：词汇与结构(单选题)

题目：For a healthy life, windows and doors should be wide and usually they should () for at least 15 hours a day.

选项：A. be kept open B. keep open C. be keeping open

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答案：A. be kept open