Here are some examples:
Correct Usage:
* "The book, which was about history, and the movie, which was based on the book, were both very interesting." Here, the first "which" refers to the book, and the second "which" refers to the movie.
* "The two candidates, both of whom were very qualified, had different views on the economy, which was the main issue in the election." The first "which" refers to the candidates, and the second "which" refers to the economy.
Incorrect Usage:
* "The car, which was red, and which was fast, was stolen." This sentence is redundant. The second "which" is unnecessary because it repeats the information already provided by the first "which."
Alternatives to Using "Which" Twice:
* Use a different relative pronoun: For example, you could replace the second "which" with "that" or "who."
* Combine sentences: You could combine the two sentences into one to eliminate the need for two "which" clauses.
* Use a different construction: You could rephrase the sentence to avoid using "which" altogether.
Overall, using "which" twice is grammatically correct, but it's important to ensure that the sentence remains clear and unambiguous.