Concept:A duplicated chromosome consists of two identical chromatids held together at one point called the centromere.Explanation:The centromere is the narrow region where the two chromatids remain attached to each other.During cell division, spindle fibres connect to the centromere, but the chromatids are never joined at the spindle.Centrioles help form spindle fibres; they do not join chromatids.Thus, the only correct description is two chromatids joined at the centromere.Answer:Two chromatids joined at the centromere.