Answer:
The given two blanks can be filled with endangered and threatened.
Step-by-step explanation:
A threatened species is considered as the one, which is at the threat of being listed as endangered or is facing the chance of turning endangered in the coming time. On the other hand, an endangered species is the one that faces the threat of becoming extinct in the coming time. Extinction is illustrated as zero population or no proof of the existence of the species on the planet.
In the given case, the number of rhinos alive is only 400 at the present time, thus, if their numbers get reduced more in the coming time, then they will face the threat of getting endangered, and soon can get extinct. However, if certain steps are taken and their numbers are prevented from getting decline further, then they can be listed under threatened list.
In a threatened species, though their numbers are more than the species that come under endangered list, if no preventive steps are taken, then these species become susceptible to come under endangered category and then soon can become extinct too.