The third man was the old man. He defeated the king with his lie. What lie did he tell the king?

1. His lie was as follows: You promised me a bag of gold.

2. His lie was this: You promised me a bag of gold.

3. His lie was that the king had promised him a bag of gold.

4. "You promised me a bag of gold."
was his lie.

5. His lie was: You promised me a bag of gold.

6. His lie was, "You promised me a bag of gold."

7. He lied to the king, "You promised me a bag of gold."

8. It was,"You promised me a bag of gold."

9. He said, " You promised me a bag of gold."

10. He told a lie to the king, "You promised me a bag of gold."
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I have written down possible answers to the question with the help of you.
Would you check the answers one more time? Can we use all those answers in colloquial expressions? Which ones do people use commonly?

I agree with all your answers except #5. I would use a comma, not a colon, after the verb "was."

The primary reason is because "His lie was" is not an independent clause (cannot be a complete sentence on its own). What I always remember is that a colon should NOT be used immediately after a verb.

"We will often use a colon to separate an independent clause from a quotation (often of a rather formal nature) that the clause introduces"
http://grammar.ccc.commnet.edu/grammar/marks/colon.htm

"Use a colon after an independent clause when it is followed by a list, a quotation..."
https://owl.english.purdue.edu/owl/resource/566/01/

I agree with Writeacher.

All of the answers you have provided are grammatically correct and convey the same message. However, in colloquial expressions, people may use different variations based on personal preference or the context of the conversation. The most commonly used expressions are:

1. "His lie was that the king had promised him a bag of gold."
2. "He lied to the king, 'You promised me a bag of gold.'"
3. "He said, 'You promised me a bag of gold.'"
4. "He told a lie to the king, 'You promised me a bag of gold.'"

These variations are commonly used in everyday speech and effectively convey the information required to answer the question.