Select the most appropriate idiom from the following options that can substitute the underlined part of the given sentence.

It is his first interview, so he has a nervous feeling.

Butterflies in his stomach

The most appropriate idiom from the following options that can substitute the underlined part of the given sentence is (1) Butterflies in his stomach.

The other options do not fit the context of the sentence.

• Butterflies in his stomach is an idiom that means to feel nervous or anxious.
• A slap on the wrist is a mild punishment.
• Tug at his heartstrings means to evoke a strong emotional response.
• Icing on the cake means something that is extra or unnecessary but makes something even better.

In the given sentence, the person is feeling nervous because it is their first interview. The idiom "butterflies in his stomach" is the most appropriate way to describe this feeling.