如果需要提高加热炉温度可以（）。
A、开大瓦斯控制阀
B、关小瓦斯控制阀
C、降低瓦斯罐的压力
D、提高炉处理量
参考答案：A
Many children, ________ parents are away working in big cities, are taken good care of in the village.[ ]
A. their
B. whose
C. of them
D. with whom
中骨盆平面狭窄容易导致胎头高直位。
