In prophase I of meiosis, chromosomes start pairing together and synapsis takes place. The process occurs during which of the following stages?

Zygotene is the stage where chromosomes begin to pair together and undergo synapsis. Synapsis is the process of pairing up homologous chromosomes along their entire length. During synapsis, a protein
structure, called the synaptonemal complex, forms between homologous chromosomes, holding them tightly together.
(1) During diplotene, the paired homologous chromosomes start to separate, and chiasmata become visible. Chiasmata are the points of crossing-over, where genetic material is exchanged between non-sister chromatids of homologous chromosomes.
(2) Leptotene is the first stage of prophase I. In this stage, the chromosomes start to condense and become visible under a microscope. They appear as long, thin, thread-like structures.
(4) Pachytene is the next stage after zygotene. In pachytene, crossingover takes place, where genetic
material is exchanged between nonsister chromatids of homologous chromosomes.