But for your help I ___
would have failed.
Correct
would fail.
will fail.
will have failed.
Explanation:
Correct Answer is: would have failed.
But for একটি phrase যার অর্থ ছাড়া বা ব্যতীত এবং ইহা past indicator তাই এর পরে past tense বসে।
You use but for to introduce the only factor that causes a particular thing not to happen or not to be completely true.
But for your help I would have failed.
তোমার সাহায্য না থাকলে আমি ফেল করতাম।