## Core Concept
The core concept being tested here is the historical demonstration of anesthetic effects, specifically focusing on ether. Ether, or diethyl ether, was one of the first substances used to demonstrate general anesthesia.

## Why the Correct Answer is Right
The demonstration of ether's anesthetic effect is attributed to **Crawford Long** and **William T.G. Morton**, but it was **William T.G. Morton** who publicly demonstrated the anesthetic effect of ether in 1846 at the Massachusetts General Hospital. This public demonstration was a pivotal moment in medical history, marking the beginning of the use of general anesthesia in surgical procedures.

## Why Each Wrong Option is Incorrect
- **Option A:** While there are numerous historical figures associated with the development and use of anesthesia, the question specifically asks for the demonstration of ether's anesthetic effect.
- **Option B:** Similarly, another figure might have contributed to the field of anesthesia but not specifically to the public demonstration of ether.
- **Option D:** This option would be incorrect for similar reasons as A and B; the correct historical figure needs to be identified with ether's demonstration.

## Clinical Pearl / High-Yield Fact
A memorable point for exams is that **William T.G. Morton** used **diethyl ether** to anesthetize a patient before a surgical procedure, marking a significant milestone in the history of anesthesia. This event is often cited as the first public demonstration of surgical anesthesia.

## Correct Answer Line
**Correct Answer: C. William T.G. Morton**