The mother of a 2-year-old child tells the nurse that her baby is using a potty seat but is still having problems toilet-training. Which of the following suggestions by the nurse would he most appropriate

A. Offer the child more praise each time.
B. Use a potty chair instead of a potty seat.
C. Focus on the "accidents" that occur during training.
D. Defer training until the child is developmentally ready.

矿井需要风量应按（）要求分别计算，并选取其中的最大值。

A、按井下同时工作的最多人数计算，每人每分钟供风量不少于4m³

B、按采煤、掘进、硐室及其它地点实际需要风量的总和进行计算

C、按使用风机的台数计算

D、按瓦斯涌出量计算