He admitted his fault (change into complex sentence)
Answers
The complex sentence refers to the sentence which contains at least one dependent clause and an independent clause. A dependent clause is the clause which cannot stand alone in its meaning on the other hand independent clause refers to the phrase which can stand alone, though both have a subject and a verb.
Therefore, when the above sentence converted into complex sentence can be written as:
He admitted that it was his fault.
Herein, "He admitted that" is a dependent clause and "It was his fault" is independent clause.
He admitted that he was at fault. The sentence written in complex form has a principal clause and one or multiple subordinate clauses.
The subordinate clauses are made by beginning the sentence with a subordinate conjunction like because, as, even though, although, or a relative pronoun like what, which, when.