12. _________ for his expertise, he would have struggled to complete the project.
(A)If it wasn’t
(B) If it weren’t
(C) If it hadn’t been
(D) If it isn’t

要不是／若不是... 搭配 「現在假設」
公式：If it were not for + N, S +would/might/could + VR eg: If it were not for air, we would die. 要不是有空氣，我們都會死.
eg: If it were not for my parents' encouragement, I would not have the passion for music. 若不是有我父母的鼓勵，我可能不會勇敢追求對音樂的熱情。

要不是／若不是... 搭配 「過去假設」
公式：If it had not been for + N, S +would/might/could + have pp eg: If it had not been for the recue team, the hiker might still have been left in the cave. 要不是有救援隊，那位健行者可能還被留在山洞裡。
eg: If it had not been for my sister's quick thinking, we would have missed the last train. 若不是有我妹妹的迅速反應，我們可能會錯過最後一班火車。