Select the most appropriate option to fill in the blank.

All of my efforts to save her life have gone in ______.

vain

The correct option to fill in the blank is vain.

The word "vain" means futile or unsuccessful. It is the most appropriate word to use in this context because it describes the speaker's efforts to save the person's life. The speaker's efforts have been unsuccessful, and they have achieved nothing.

The other options are not as appropriate.

• Vein means a blood vessel that carries blood away from the heart. This does not make sense in the context of the sentence because the speaker is not talking about blood vessels.
• Van means a small truck or van. This does not make sense in the context of the sentence because the speaker is not talking about vehicles.
• Vane means a weather vane. This does not make sense in the context of the sentence because the speaker is not talking about weather vanes.