Final answer:
The character in the Mark Twain excerpt faces an external conflict of maintaining composure under scrutiny. Evidence of the conflict is indicated by Twain's reaction to the pressure from Mr. Bixby's actions. Twain responds by trying to manage his self-doubt and to stay calm.
Step-by-step explanation:
The external conflict the character faces in the Mark Twain excerpt is his struggle to remain composed and confident in his ability to run a crossing while being unnerved by Mr. Bixby sending additional people to watch him. The line from this passage which serves as evidence supporting the conflict might be one where Twain acknowledges his growing nervousness or second-guessing as the crowd sent by Mr. Bixby grows. Twain responds to the conflict by grappling with his self-doubt and attempts to maintain his composure despite the increased pressure.
The main conflict that Twain faces is external, as it's caused by his environment and the actions of another character, Mr. Bixby, which affects his mental state. A story's climax usually reflects the highest point of such tension, which in this scenario could be Twain's ultimate action in running the crossing, successful or not, under the scrutinizing eyes set upon him.
Understanding the difference between internal conflict and external conflict is vital in analyzing literature. Internal conflicts involve a character's emotional or mental struggles, while external conflicts arise from the character's external circumstances, opposing forces, or interactions with other characters.