Complete the sentence:If they had followed the instructions, ____________________

• If যুক্ত clause টি Past Perfect tense এ থাকলে অপর clause টির Subject এর পরে might have/ would have/ could have বসে এবং verb টির Past Pasrticiple হয়।
- Structure: If + Past Perfect tense + Perfect Conditional (would/could/might + have + V₃).
Examples:
- If I had studied harder, I would have passed the exam.
- If she had told me earlier, I would have been able to help her.
- If they had listened to the weather forecast, they wouldn't have gone hiking in the storm. 

Complete Sentence: If they had followed the instructions, the experiment would have been successful.

Source: Advanced Learner's English Grammar & Composition by Chowdhury & Hossain.