Some editions of Building Skills for Proficiency sell the answer key as a physical booklet through Turkish bookstores (e.g., D&R, Kitapyurdu, Nobel Kitap). Check ISBNs.
If you search for the PDF answer key online, you will encounter a few hurdles: Some editions of Building Skills for Proficiency sell
Cesur Öztürk’s Building Skills for Proficiency (often abbreviated as BSP) is widely used in Turkey’s higher education preparatory programs. The book focuses on advanced grammar, academic vocabulary, reading comprehension, and cloze tests. A persistent demand among students is the PDF version of the answer key, as self-assessment is critical for independent study. However, the answer key is typically restricted to instructors or sold as a separate booklet. Some editions of Building Skills for Proficiency sell