What is important to write on a strain stock label?

Correct answer: Strain name, plasmid, date and marker

A strain-stock label is part of traceable laboratory record keeping and sample identification. It should provide enough information to distinguish one biological sample from another and to reconstruct its history. The strain name identifies the host background, the plasmid identifies the introduced genetic material, the date helps track preparation and storage age, and the selectable marker or relevant phenotype supports later verification. Therefore option A is correct. A well-labelled stock reduces mix-ups, prevents use of an unknown culture, and improves reproducibility and safe handling. Water taste, plate smell, or protein colour alone cannot identify a strain or establish what genetic material it contains.