Correct Answer: (e) both (b) and (d)
Solution:(b/d) Both options (b) and (d) are correct for the given phrase.
The phrase, 'be as sharp as a tack' means to be very intelligent, quick-witled, perceptive or shrewd. It suggests that someone is mentally alert and able to think clearly or solve problems effectively. "Tack' emphasizes the idea of sharpness in a figurative sense here.