Final answer:
Chromosomes first become visible in the leptotene stage and the synaptonemal complex is complete in the pachytene stage of prophase I in meiosis.
Step-by-step explanation:
Stages of Chromosome Visibility and Synaptonemal Complex Formation
Chromosomes become first visible during the leptotene stage of prophase I in meiosis. At this stage, the chromatin starts to condense, making the chromosomes visible under a microscope.
The synaptonemal complex, a protein structure that plays a critical role in the pairing of homologous chromosomes, is complete in the pachytene stage. During pachytene, homologous chromosomes are fully synapsed, and the synaptonemal complex holds them together along their length, supporting the process of crossing over. Therefore, the correct answer to the student's question is b) Leptotene, pachytene.