A bivalent in metaphase I consists of :

Four chromatids and two centromeres .

The correct answer is Option (2)-Four chromatids and two centromeres.

Meiosis involves two sequential cycles of nuclear and cell division called meiosis I and meiosis II but only a single cycle of DNA replication.

Meiosis I is initiated after the parental chromosomes have replicated to produce identical sister chromatids at the S phase .

Meiosis involves pairing of homologous chromosomes and recombination between non-sister chromatids of homologous chromosomes.

Four haploid cells are formed at the end of meiosis II.

Meiosis I
Prophase I: Prophase of the first meiotic division is typically longer and more complex when compared to prophase of mitosis. It has been further subdivided into the following five phases based on chromosomal behaviour, i.e., Leptotene, Zygotene, Pachytene, Diplotene and Diakinesis.

Metaphase I: The bivalent chromosomes align on the equatorial plate . The microtubules from the opposite poles of the spindle attach to the kinetochore of homologous chromosomes. They consist of 4 chromatids and 2 centromeres.