One common advantage of a long-term investment is

higher return.
lower risk.
higher liquidity.
lower liquidity

The answer is higher return.

One common advantage of a long-term investment is higher return.

Explanation: Long-term investment refers to investment instrument such as bonds, stocks, real estate and so on that matures after many years. Long-term investment are also assets that can be held for more than a year. Long-term investors encounter series of risk in pursuit of higher returns or reward.

Higher return means gain generated from an investment over a period of time.

the answer your looking for is c. : )