Explanation:
Synapsis is the process during meiosis where homologous chromosomes (chromosomes that are similar in size, shape, and genetic content, one from each parent) pair up and align closely. This occurs during prophase I of meiosis.
Other options:
Male and female gametes: Fusion of gametes occurs during fertilization, not synapsis.
mRNA and ribosomes: This is part of translation, not synapsis.
Spindle fibers and centromere: This is part of the process of chromosome movement during cell division but not synapsis.
Thus, two homolog chromosomes is the correct answer.