Final answer:
The correct option in the final answer is b. During prophase I of meiosis I, homologous chromosomes pair tightly in a process called synapsis, which involves the formation of a synaptonemal complex, facilitating crossing-over.
Step-by-step explanation:
During prophase I of meiosis I, homologous chromosomes undergo several processes as they prepare for the subsequent stages of meiosis. Early in prophase I, homologous chromosomes come together in a process called synapsis. The chromosomes are bound tightly together and in perfect alignment by a protein structure known as a synaptonemal complex.
The synaptonemal complex facilitates the exchange of genetic material in an event known as crossing-over or recombination, where non-sister chromatids of homologous chromosomes exchange segments of DNA, creating new combinations of alleles. Therefore, the correct answer to the student's question is option b) Synapsis.