Refer to figure.
Synoptic pressure patterns include several named features beyond the basic high and low. 

A col is a region of relatively uniform pressure that lies between two areas of high pressure and two areas of low pressure arranged alternately (high, low, high, low going around the col). The pressure gradient in a col is weak and the isobars are widely spaced or absent. 

Weather in a col is often variable and unsettled: it may be clear and calm in summer but can produce fog, thunderstorms, or general instability because the lack of organised pressure gradient means the atmosphere is susceptible to local heating effects. 

Col → CORRECT. A col is the area of slack or neutral pressure located between two anticyclones and two depressions arranged alternately on the synoptic chart. It is characterised by weak and variable winds, poor horizontal visibility, and weather that can be unpredictable due to the absence of a dominant pressure system.

Ridge → INCORRECT. A ridge is an elongated extension of a high-pressure area projecting into a region of lower pressure. It is not the area between two highs and two lows but rather the extension of a single high-pressure system.

Trough → INCORRECT. A trough is an elongated extension of a low-pressure area projecting into a region of higher pressure. It often brings cloud and precipitation and may be associated with frontal systems. 

Saddle → INCORRECT. Saddle is sometimes used as an alternative term for col in certain meteorological traditions, but col is the correct and precise ATPL examination term. In standard ICAO and EASA meteorology syllabus the correct answer is col.