Concept:The labelled part II is one half of a duplicated chromosome, known as a chromatid.Explanation:A chromosome that has replicated consists of two identical halves joined at the centromere.Each of these halves is called a chromatid.The part labelled II points to one of these halves, not to an organelle or cell structure.Therefore, it cannot be a centriole, chloroplast, or tonoplast.Answer:C. chromatid
