Answer:
They are both mammals with tails.
Explanation:
Hope this helps!
Your question isn't the most clear, but I think your answer is rocks, or more specifically phosphorous rich rocks because the phosphorous will mix with the sediments on the river's/lake's ground forming phosphorous rich rocks.
That means that It'll become a phosphate mineral and later become phosphorous again when the minerals weather.
Hope it helped,
BioTeacher101
First blank: The mobility of their hosts same goes for the second one :)
Antigens determine blood type