聚碳酸酯的应力-应变曲线属以下哪一类()
A、硬而脆
B、软而韧
C、硬而韧
参考答案:C
Life would be happier if we could only be born at the age of eighty and ________reach eighteen.
A.entirely
B.gradually
C.finally
D.rapidly
慢性支气管炎急性发作期是指多长时间内出现脓性或粘液脓性痰,痰量明显增加等症状()。
A.3天
B.1周
C.2周
D.3周
E.1个月