His【memory记忆】is very poor.He has read the text many times but he still can't remember it.Please read the 【instructions说明书 （必须用复数）】carefully before you take the medicine.祝开心....为什么必须用复数？你查查词典就知道了，可以看作固定用法。或者通俗地理解为：说明一般都是分为几条的。词典上的例句：Read the instructions on the bottle before you take the medicine.