If they had taken my advice, they ____________ that mistake.

• শূন্যস্থানে সঠিক উত্তর হবে - would not have made.
- Complete sentence: If they had taken my advice, they would not have made that mistake.

• বাক্যটি third conditional এ আছে।
- Third Conditional এর নিয়মানুযায়ী,
- If-এর পর Past Perfect Tense থাকলে পরবর্তী Sentence টিতে Past Perfect Conditional বসে।
অর্থাৎ, would have/could have + verb-এর Past Participle form হয়।

Example: 
Structure: If + Past Perfect Tense + Past Perfect Conditional
Example: If you had come, I would have gone there.