Buying a call option, also known as a long call, is a capital-efficient strategy for obtaining upside exposure to an asset. Here's why:

1. *Leverage*: Call options provide leverage, allowing you to control a large position with a relatively small amount of capital.

2. *Lower capital requirements*: Buying a call option requires a much smaller investment compared to buying the underlying asset outright.

3. *Upside potential*: Long calls offer unlimited upside potential, as the option's value increases with the price of the underlying asset.

4. *Limited risk*: The risk is limited to the premium paid for the option, making it a capital-efficient way to gain exposure to an asset.

5. *Flexibility*: Long calls can be used to speculate on price movements or to hedge against potential losses in a physical position.

For example, let's say you want to gain exposure to 100 shares of XYZ stock, currently trading at $50. Instead of buying the shares outright, you could buy a call option with a strike price of $50 for $5. This would give you the right to buy the shares at $50, while only requiring a capital outlay of $500 (5 x $100).

Keep in mind that options trading involves risk, and it's essential to understand the terms and conditions before entering into any options transaction.