英语定语从句可以用于写开题报告中对研究对象、目的、方法等的描述。以下是一些写英语定语从句的方法和示例：
研究对象：描述需要研究的对象或者受试者等。
The participants who were recruited for this study were college students.
The subjects that were selected for the experiment were randomly assigned to two groups.
The patients whom we interviewed were all diagnosed with the same disease.
研究目的：描述研究的目的、假设或者研究问题等。
The main objective of this study, which is to investigate the effects of exercise on mental health, has not been fully explored.
The hypothesis that there is a significant relationship between sleep deprivation and cognitive performance was tested in this experiment.
The research question, which focuses on the impact of social media on adolescent mental health, is of great interest in the field of psychology.
研究方法：描述采用的研究方法、工具或者分析技术等。
The data that were collected in this study were analyzed using SPSS software.
The questionnaire that was developed for this survey consisted of 20 questions and took approximately 30 minutes to complete.
The experimental design that was used in this research involved a within-subjects design.
以上是写英语定语从句的一些方法和示例，可以根据自己的研究对象、目的和方法等情况进行适当的调整和修改。