Frank was bound hand and foot and tightly blind-folded, but unharmed. A. bound by B. bound in C. bound to D. No improvement

The correct answer is D. No improvement.

The sentence

“Frank was bound hand and foot and tightly blind-folded, but unharmed” is grammatically correct and conveys the intended meaning clearly. The word “bound” is used in the sense of “tied up” or “confined.” The phrase “hand and foot” indicates that Frank was tied up with his hands and feet. The phrase “tightly blind-folded” indicates that Frank was blindfolded so that he could not see. The phrase “but unharmed” indicates that Frank was physically unharmed, despite being tied up and blindfolded.

The other options are not as clear or concise as the original sentence. Option A, “bound by,” could be interpreted to mean that Frank was bound by a rope or other object. Option B, “bound in,” could be interpreted to mean that Frank was bound inside of something, such as a box or a room. Option C, “bound to,” could be interpreted to mean that Frank was bound to something, such as a chair or a tree.

Overall, the original sentence is the best option because it is grammatically correct, clear, and concise.