The correct translation of ‘মানবতর বৃহত্তর কল্যাণে বিজ্ঞানের নিয়োজিত করতে হবে’ is-

We have to apply science to the greater interest of human

We have apply science to the greater well-being of humanity

We should apply science to the greater profit of humanity

We have to apply science to the greater well-being of humanity