The Bengali word for 'thank you' is 'Dhonnobad' (ধন্যবাদ). Option B 'Dhenabad' has a transliteration error ('e' instead of 'o' in first syllable) but is clearly the intended correct answer. 'dhanyavaad' is Hindi, 'Shukriya' is Urdu-influenced, and 'dhan-vahd' is garbled.