The correct answer is (d) realistic.
Idiom: "Down to earth" — describes a person who is practical, sensible, and realistic; someone who does not have exaggerated ideas or fantasies about themselves or life.
Example: "She is very down to earth — she always gives practical advice."
Bangla meaning: বাস্তববাদী, ব্যবহারিক জ্ঞানসম্পন্ন।
✗ "close to nature" — this would be "close to the earth/nature" literally.
✗ "thrown to ground" — this is the literal meaning, not the idiomatic one.
✗ "hopeful" — unrelated to the idiom.
Source: Oxford Idioms Dictionary; Longman Dictionary of Contemporary English.