Correct Answer: Fruitless

Solution : The correct choice is the first option.

Explanation :
Fruitless and futile both convey the idea of being unsuccessful or producing no result. In this context, the efforts of the doctors led to a futile end, meaning that despite their hard work, it was unsuccessful in saving the patient's life. Fruitless aligns perfectly with this meaning, as it denotes an effort that doesn't yield any desirable outcome.

The meanings of the other options are as follows:

• Enriching means to improve or enhance something, often in a positive manner.
• Startling means surprising or shocking.
• Terrifying means causing extreme fear or dread.

Therefore, the correct answer is fruitless.