Awave oscillates 50 times per second. what is its frequency?

You just told us how many times per second the wave oscillates. That's a definition of frequency. So the frequency of this wave is 50 per second or 50 hertz.

Wow good luck with that answer

How is it possible that phylogenies based on sequences from nuclear genomes and organellar genomes (i.e., chloroplasts and mitochondria) from the same group of species yield phylogenetic trees with different branching orders?   answer :   the genome of the endosymbiont is more closely related to members of the group in which it originally evolved, while the nuclear genome of the engulfing organism has its own evolutionary trajectory.