In the excerpt below, the nonrestrictive relative clause has been reduced, following the principles of the relative pronoun + verb to be deletion r...

In the excerpt below, the nonrestrictive relative clause has been reduced, following the principles of the relative pronoun + verb to be deletion rule. Choose the option that best rephrases the statement below, while also eliciting the previously deleted relative pronoun and verb to be.


But experts say the wildfires have highlighted one of the main weaknesses in the program that is the small size of the so-called buffer pool, (...).
But experts say the wildfires have highlighted one of the main weaknesses in the program which is the small size of the so-called buffer pool, (...).
But experts say the wildfires have highlighted one of the main weaknesses in the program - whose is the small size of the so-called buffer pool, (...).
But experts say the wildfires have highlighted one of the main weaknesses in the program - which is the small size of the so-called buffer pool, (...).
But experts say the wildfires have highlighted one of the main weaknesses in the program, in which is the small size of the so-called buffer pool, (...).