供电质量主要是用()标准来衡量。
A、供电半径
B、供电电压
C、供电频率
D、供电可靠性
参考答案:B, C, D
根据课文内容判断下面的句子是否正确,正确的画“√”,错误的画“×”。
( ) 1. Aunt Wanrong is my mother's sister.
( ) 2. Uncle Zhiwei is my aunt's wife.
( ) 3. Aunt Meiping is my uncle's wife.
( ) 4. Jing is my Uncle Dachao's and aunt Meiping's son.
机翼升力始终向上,并垂直地面。