Answer:
a. 50 thousand
Explanation:
<u>From the answer option, the closest true number is around 50 thousand.</u>
It is estimated there are around 62 to 69 thousand species of vertebrates in the world.
<u>Vertebrates are one of the major groups of animals and they are the ones that have the backbone</u>. In the group of vertebrates, we can divide animals into further subgroups of amphibians, mammals, reptiles, fish, and birds. Therefore, we can see there is a large number of animals that we know of which are included in the vertebrates group.