1. He refused to help me.

2. He rejected to help me.
3. He dislikes to help me.

4. He refused helping me.
5. He rejected helping me.
6. He dislikes helping me.

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Which expressions do we have to use?
The verbs, reject and refuse take 'to infinitive' as an object. Am I right?

1 is correct. 2 and 3 are incorrect.

4 is incorrect. 5 and 6 are okay, but don't mean the same as 1.

You are correct! The verbs "reject" and "refuse" are followed by the "to infinitive" form of the verb as an object. Let's break down each of the expressions you've provided:

1. "He refused to help me." - This is the correct expression. "Refused" is followed by the "to infinitive" form of the verb "help."

2. "He rejected to help me." - This expression is not correct. Instead, you should use "rejected" followed by the "to infinitive" form of the verb "help." So it should be: "He rejected to help me."

3. "He dislikes to help me." - This expression is not correct. The verb "dislikes" is not typically followed by the "to infinitive" form. Instead, you should use "dislikes" followed by the gerund form of the verb "helping." So it should be: "He dislikes helping me."

4. "He refused helping me." - This expression is not commonly used. "Refused" is typically followed by the "to infinitive" form of the verb, as mentioned earlier. So the correct expression should be: "He refused to help me."

5. "He rejected helping me." - This is the correct expression. "Rejected" is followed by the gerund form of the verb "helping."

6. "He dislikes helping me." - This is the correct expression. "Dislikes" is followed by the gerund form of the verb "helping."