What is the purpose of size selection in restriction digestion?

Correct answer: Selecting desired size fragment

The direct answer is A: size selection is used to select the desired-size DNA fragment. After restriction digestion, several fragments of different lengths may be present. In gel-based size selection, the fragments are separated by electrophoresis, the band at the required size is identified with a ladder and expected map, and that band is excised for purification. This removes unwanted fragments and improves the chance that the intended insert or vector is used in cloning. Option A is correct because it describes the purpose directly. Option B is wrong because size selection does not primarily destroy the enzyme; enzyme removal is a separate cleanup concern. Option C is wrong because methylation changes DNA chemistry and is not the aim of choosing a size band. Option D is wrong and unsafe because gel is never tasted and tasting has no scientific purpose. Select the correct size, but also check band identity and DNA quality. Memory cue: size selection keeps the right length and removes the wrong pieces.