If they had invested in renewable energy sources a decade ago, they __________ significantly ___________ their carbon footprint and contributed to a more sustainable future.

• প্রশ্নে উল্লিখিত Sentence টি একটি 3rd Conditional sentence এর উদাহরণ।

Structure: If + past perfect tense + would/could/might + have + past participle.

• Third conditional এর নিয়মানুযায়ী -
- Conditional-এ subordinate conjunction 'if' এর পর Past Perfect Tense হলে,
তার পরবর্তী Clause- এ would/could/might + have + Verb-এর Past Participle form হবে।

Complete sentence: If they had invested in renewable energy sources a decade ago, they would have significantly reduced their carbon footprint and contributed to a more sustainable future.

Example Sentence:
1. If I had studied harder, I would have passed the exam.
2. If they had left earlier, they wouldn't have missed the train.

- These are the examples of the Third Conditional.