Explanation

Financial asset return time series typically exhibit several common characteristics:

1. No Trend: Asset returns generally do not exhibit any systematic upward or downward trend over time. This is consistent with the efficient market hypothesis where prices follow a random walk.

2. Leptokurtic Distributions: Most asset return distributions are leptokurtic, meaning they have fatter tails and higher peaks than a normal distribution. This contradicts option D which states "thin tails."

3. Low Correlation: Asset returns typically show low serial correlation, meaning returns from one period are not strongly correlated with returns from previous periods.

4. Weak Stationarity: While not perfectly stationary, many financial time series can be considered weakly stationary (constant mean and variance over time) after appropriate transformations.

The correct answer is C because the absence of trend is a well-documented characteristic of financial asset returns, consistent with market efficiency theories.