1. A过去几年里研究表明维生素D可能增加血清素，它是影响我们情绪的主要神经传导物质之一， 从而有助于缓解情绪障碍，高考英语题。
sugested 后接两个宾语从句that Vitamin D...our mood 和 that it helps to relieve mood disorders
2. A.有些人不吃饭或者仅吃一点，有可能会出现人体生长和保持健康所需的营养物质丧失的状况发生。
...conditions which/that rob the body of ...定语从句缺主语，修饰conditions,
...nutrients (which/that) it/the body needs to grow and stay healthy
3. D. 动词不定式to keep company 作定语修饰some people
you have some people to keep company 你有一些要陪伴的人
其余的选项必须这样或是另外的意思：（have使役动词）
you have some people keep company with you你让一些人陪伴你 you have some people keeping company with you 你让一些人一直陪伴你
you have some people kept company 你让一些人被陪伴
[高考英语复习指导]