In which host is colony picking done easily?

Correct answer: Bacterial host

The governing concept is the use of a competent microbial host for cloning and selection. Bacterial cells carrying different recombinant vectors can be spread on a solid agar medium, where each viable transformed cell multiplies into a visibly separate colony. A researcher can therefore pick one colony with a sterile loop and grow it as an individual clone for further testing. Option A is correct because bacterial growth on agar provides discrete, accessible colonies. Direct human muscle, a water sample, and a fat layer do not normally provide isolated recombinant colonies under standard cloning conditions, so options B, C, and D are unsuitable distractors.