题目内容

-John sings so well. Has he ever been trained?-No. He learns all by himself. He _________goes to any training class.

A. usually
B. often
C. never
D. even

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–Miss Gao is very popular with her students.-Yes, Her classes are _________lively and interesting.

A. seldom
B. never
C. sometimes
D. always

在管内稳定的湍流区域，热阻主要存在于：

A. 主流区域
B. 湍流边界层
C. 管内均匀分布
D. A或B都有可能

当导热系数λ和特征长度L相同时，努塞尔数可以表征对流传热的强弱。（）

A. 对
B. 错

雷诺数反映了流体强制对流时，惯性力和粘性力的相对大小。（）

A. 对
B. 错