What looks like a wall of text is actually just a basic introduction. Important stuff.

This is a good introduction. Gas-liquid chromatography has many variations, but the most basic separation is based on volatility. A reliable rule is that the more volatile the sample, the lower the retention time.

A more in-depth treatment. The MCAT likes to bring procedure details into the work-flow description in a passage. Foreknowledge keeps your footing in the passage. It helps keep your head clear. The question about the technique will often not be so difficult.