在备战2020年高考的过程中，掌握一定量的核心高频词汇是提高英语成绩的重要基础。这份包含688个核心高频词汇的清单，涵盖了历年高考中出现频率较高的词汇，是考生复习和备考不可或缺的工具。

以下是一些精选词汇及其例句：

1. accomplish - vt. 完成；实现

- Example: She accomplished her goal of running a marathon last year.

2. beneficial - adj. 有利的；有益的

- Example: Regular exercise is beneficial to both physical and mental health.

3. contribute - vi. 捐献；贡献 vt. 捐助；投稿

- Example: He contributed a large sum of money to the charity.

4. determine - vt. 决定；确定

- Example: The weather will determine whether we can go hiking tomorrow.

5. environment - n. 环境；外界

- Example: Protecting the environment is everyone's responsibility.

6. frequent - adj. 经常发生的；频繁的

- Example: Frequent communication is essential for maintaining a good relationship.

7. improve - vt. 改善；改进 vi. 改进；变得更好

- Example: Continuous learning can improve our skills and knowledge.

8. maintain - vt. 维持；保持

- Example: It is important to maintain a healthy lifestyle.

9. opportunity - n. 机会；机遇

- Example: Seize the opportunity when it presents itself.

10. progress - n. 进步；进展 vi. 进步；发展

- Example: We have made great progress in this project.

通过反复背诵这些词汇，并结合实际语境进行练习，可以有效提升词汇量和语言表达能力。此外，建议将这些词汇融入日常学习和生活中，形成自然的语言记忆模式。

希望这份词汇清单能够帮助你在高考英语中取得优异的成绩！