参考答案：
87.Because of the noise outside, Nancy had great difficulty in focusing on her experiment (集中注意力在实验上)
88.The manager never laughed; neither did she lose temper (她也从来没有发过脾气)
89.We look forward to being invited to attend the opening ceremony(被邀请出席开幕式)
90.It is suggested that the air conditioner should be installed beside the window(要安装在窗户旁)
91.The 16-year-girl decided to travel abroad on her own despite her parents strong disagreement(她父母的强烈反对)
答案解析：
87题语法点为have difficulty in doing sth，另外focus on为四级高频词组需要牢记。
88题为neither 放在句首的倒装句，并且是部分倒装，把助动词did 提前，另外发脾气lose temper 为四级核心高频词组。
89题短语look forward to doing sth中的to为介词，后接的动词需要变成动名词，另外考察了被动的用法：be invited to do sth; 开幕式为the opening ceremony固定搭配。
90题为It is suggested that的虚拟语气，是四级重要考查语法点。that后面的句子结构为“主语+should+do sth”，此句中air conditioner“安装在窗户旁”暗含了被动含义，需要写成be installed。
91题考查despite后接名词，表让步含义。
