To solve this problem, we need to determine what a scrubber in the exhaust of a chemical industrial plant removes. Let's analyze each option:$\newline \bullet$Option 1: Gases like sulphur dioxide.$\newline$ - Scrubbers are devices used to remove pollutants from industrial exhaust streams.$\newline$ - They are particularly effective at removing gaseous pollutants such as sulphur dioxide (SO$_2$).$\newline$ - Therefore, this option is correct.$\newline \bullet$Option 2: Particulate matter of the size 5 micrometer or above.$\newline$ - While scrubbers can remove some particulate matter, they are primarily designed for gaseous pollutants.$\newline$ - This option is not the primary function of a scrubber.$\newline \bullet$Option 3: Gases like ozone and methane.$\newline$ - Scrubbers are not typically used to remove ozone and methane.$\newline$ - These gases require different methods for removal or reduction.$\newline$ - Therefore, this option is incorrect.$\newline \bullet$Option 4: Particulate matter of the size 2.5 micrometer or less.$\newline$ - Scrubbers are not primarily used for removing fine particulate matter.$\newline$ - Other technologies, such as filters, are more effective for this purpose.$\newline$ - Therefore, this option is incorrect.$\newline$Based on the analysis, the correct answer is Option 1: Gases like sulphur dioxide.