Select the most appropriate meaning of the underlined idiom.
Despite multiple obstacles, she continued with her endeavour, demonstrating that she has nerves of steel.

The correct option is An absence of fear or anxiety.

Explanation:
The idiom "nerves of steel" refers to having extraordinary courage, bravery, and emotional control, demonstrating an absence of fear or anxiety even in very stressful, dangerous, or challenging situations.

In the context of the sentence: "Despite multiple obstacles, she continued with her endeavour, demonstrating that she has nerves of steel," the idiom describes her ability to remain calm, resolute, and fearless despite facing numerous obstacles.

Thus, the most appropriate meaning of the underlined idiom is "An absence of fear or anxiety".