A woman tells the nurse that her 6-year-old daughter has severe nosebleeds. Which of the following instructions should the nurse give this woman to manage nosebleeds

A. Help the child assume a comfortable position with her head tilted backward.
B. Tilt the child’s head backward and place firm pressure on the nose.
C. Help the child lie on her stomach and collect the blood on a clean towel.
D. Place the child in a sitting position with her neck bent forward and apply firm pressure on the nasal septum.

对于0.1mol•L^-1的Na₂S溶液，下列判断正确的是（　　）

A．溶液中阴离子浓度的大小顺序：c（S^2-）＞c（OH^-）＞c（HS^-）

B．c（Na⁺）=2c（S^2-）+c（OH^-）+c（HS^-）

C．向Na₂S溶液中加水稀释，其所有离子的浓度都减小

D．向溶液中加入少量NaOH固体，能促进水的电离