非谓语动词主要包括to do, -ing和-ed三种形式，可是其用法非常广泛，它不仅是高考单项选择题测试的一个重点，而且也是完形填空、阅读理解、短文改错的重要考查内容。为了能更好地掌握非谓语动词的用法，笔者在教学实践中总结出十条实用的解题原则，并且还用相关的题目来解释这些原则。根据这些原则，相信同学们可以轻松地应对非谓语动词。
原则一：两个句子必须要用连词连接，如果没有连词连接，则需要用非谓语动词
例1. _________ many times, but he still couldn’t understand it.
A. Having been told B. Having told C. He had been told D. Though he had been told
例2._________ many times, he still couldn’t understand it.
A. Having been told B. Having told C. He had been told D. Though he had told
解析：例1中有连词but连接，表明前后都是句子，所以答案为C。
例2中后面是一个句子，而且没有连词，所以前面不是句子，应该用非谓语动词，根据句意此处为被动，所以答案为A。
