What is the basic measure of how much an option price changes for a one point move in the underlying price?

The correct measure of how much an option price changes for a one-point move in the underlying price is known as Delta. Delta quantifies the sensitivity of an option's price to changes in the price of the underlying asset. Specifically, it indicates how much the price of the option is expected to increase or decrease when the underlying asset's price moves by one unit.

Gamma, while also a crucial measure in options pricing, defines the rate of change of Delta with respect to changes in the underlying price. It reflects the curvature of the relationship between the underlying price and the option's price and provides insight into how Delta itself may change as the underlying price fluctuates.

Vega measures the sensitivity of an option's price to changes in the volatility of the underlying asset, while Theta quantifies the time decay of the option's price as it approaches expiration. Thus, they address different dimensions of options pricing and do not directly represent the immediate impact of a change in the underlying asset's price on the option itself.