Many viewers were shocked when chat show host Jerry Fox fainted while ______.

The sentence describes an event happening during a live broadcast of a chat show. The options indicate the state of the host.

1. Understand the context: The event (fainting) occurred during a live television show.

2. Evaluate the options: "On air" means being broadcast live, "in show" is vague, and "in the act" refers to being caught doing something.

3. Choose the most suitable phrase: "On air" accurately describes the situation of the host fainting during a live broadcast.