Understanding Seasonality in Time-Series Analysis

A company, XYZ Corp, is analyzing its quarterly sales data for the past five years to understand seasonal patterns in sales performance. The company noticed that its sales peak during the last quarter of each year, correlating with the holiday season, and dip during the first quarter of the year. To quantify this seasonality, XYZ Corp fits a seasonal decomposition model to its time series data.

When applying seasonal decomposition of time series (STL), which of the following can be inferred about the seasonality component?