— ___________________

— Once or twice a week.

A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.

患者女，56岁，稳定型心绞痛病史，今与邻居争吵时突然发生心前区压榨样疼痛，自行舌下含服硝酸甘油作用是（　）。