To solve this problem, we need to identify the unit used to measure the thickness of ozone in a column of air in the atmosphere. Let's analyze each option:$\newline \bullet$Option 1: Dobson units - Dobson units are the most common unit for measuring the total amount of ozone in a column of the atmosphere. One Dobson unit (DU) is defined as 0.01 mm thickness of ozone at standard temperature and pressure.$\newline \bullet$Option 2: Decibels - Decibels are a unit of measurement for sound intensity, not related to atmospheric ozone.$\newline \bullet$Option 3: Decameter - A decameter is a unit of length equal to 10 meters, not used for measuring ozone thickness.$\newline \bullet$Option 4: Kilobase - Kilobase is a unit used in genetics to measure the length of DNA or RNA, not related to atmospheric measurements.$\newline$Based on the analysis, the correct unit for measuring the thickness of ozone in the atmosphere is Dobson units.$\newline$Therefore, the correct option is Option 1: Dobson units.