What aspect of an option does "Vega" primarily affect?

Vega is a crucial measure in options trading that quantifies the sensitivity of an option's price to changes in implied volatility of the underlying asset. When implied volatility increases, the premiums of options tend to rise, and vice versa. Thus, an option with a high vega will experience larger price changes in response to shifts in implied volatility compared to one with a low vega. This characteristic makes vega particularly significant for options traders, as it helps them understand how changes in market sentiment about future volatility can impact the value of their options positions.

The other choices pertain to different aspects of options pricing. The underlying asset price influences the intrinsic value of the option but is not directly affected by vega. The time until expiration relates to theta, which measures time decay, rather than vega’s focus on volatility. The strike price is part of an option's structure but does not relate to how price is affected by changes in implied volatility, which is the domain of vega.