下列哪种营养素是产热营养素 A．蛋白质 B．维生素 C．纤维素

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问题单项选择题

下列哪种营养素是产热营养素

A．蛋白质
B．维生素
C．纤维素
D．无机盐
E．微量元素

答案

参考答案：A

解析：蛋白质、糖类、脂肪可供给能量，维生素和矿物质在体内不能供能。

阅读理解

阅读课文,判断正(T)误(F)

( )1. In the town where the black lived,they could live and work freely.

( )2. Mandela helped Elias get the correct papers so he could stay in Johannesburg.

( )3. In thirty years,the black in South Africa lost almost all their rights and progress gradually.

( )4. Only those who were born in Johannesburg could get a passbook there.

( )5. Elias was in danger of losing his job when he didn't have a passbook.

填空题

异步电动机可以通过改变电源频率、改变（）和改变磁极对数三种方法调速。