The painting which is hanging in the lobby was donated.
Ahanging in the lobby was donated
Bwhich hangs in the lobby has been donated
Cthat is hanging in the lobby was donated
Din the lobby, which is hanging, was donated
Answer & Solution
Correct answer: C. that is hanging in the lobby was donated
1. 'That' for restrictive clauses; 'which' needs a comma.
_Source: 501-GMAT-Questions Ch 3 Sentence Correction_