Correct answer:
"<span>B- homologous chromosomes join together to form tetrads during prophase I"
</span>It is during prophase I that homologous chromosomes join together (<span>synapsis)</span> and form tetrads - four chromatids are together in the new structure of two chromosomes - and this is the reason why crossing-over occurs in this phase. It is in this tetrad that both arms of both chromosomes may crossover and matching regions exchange places. This process results in homologous chromosomes recombination leading to genetic variability.
Mitosis determines the traits presented in the cluster of cells.
There are around 350,000-600,000
The phenomenon is called an equinox. More specifically when it is September it is called the autumnal equinox ,and when it is March it is called the vernal equinox. Hope this helped!
