1. He delayed leaving for Paris.

2. He delayed to leave for Paris.
(Which one is right?)

3. He refused to go / going back home.
4. He rejected to go / going back home.
(Do we have to use 'to go' or' going' in #3 and #4?)

#1 is correct.

In #3 and #4 you could u se either.

Sra

Sra is correct for 3 and 4 -- both are grammatically correct.

I think, however, that we use "to go" in that construction far more than "going."

1. "He delayed leaving for Paris." is the correct sentence.

To explain why, let's break this sentence down:
- The verb "delayed" means to postpone or put off.
- "Leaving" is a gerund form of the verb "leave", which acts as a noun in this sentence.
- "For Paris" is a prepositional phrase indicating the destination.
So, when you say "He delayed leaving for Paris," you are saying that he postponed his departure for Paris. This sentence is grammatically correct and sounds natural.

2. "He delayed to leave for Paris." is not correct.
In this sentence, the verb "delayed" is followed by the infinitive "to leave." However, the verb "delayed" already implies a postponement or a delay, so using the infinitive "to leave" is redundant and awkward. It is more appropriate to use a gerund form of the verb, as shown in the correct sentence above.

3. "He refused to go back home." is the correct sentence.
To explain why, let's analyze this sentence:
- The verb "refused" means to decline or say no to something.
- "To go" is the infinitive form of the verb "go," which expresses the action of going.
- "Back home" is a prepositional phrase indicating the destination.
So, when you say "He refused to go back home," you are stating that he declined the idea or request of going back home. This sentence is grammatically correct and conveys the intended meaning.

4. "He rejected to go back home." is not correct.
In this sentence, the verb "rejected" is followed by the infinitive "to go." However, the verb "rejected" does not typically take an infinitive complement. Instead, it is more common to use the verb "refused" to express the idea of declining or saying no to something. Therefore, the correct sentence would be "He refused to go back home."