Answer:
<u>A common element among all the river valley civilizations was irrigation systems that moved water to crops and settlements</u>
Explanation:
- <u>River Valley civilizations where the civilizations that were found on the banks of the river like the Mesopotamia ,Indus valley civilization.</u>
- <u>These civilization where agriculture based civilization as they depended on river for drinking water and irrigational activities</u>
Explanation:
HIV virus is an RNA virus
Answer:
A dolphin or whale.
Explanation:
It is a mammal, but is mistaken for a fish since it lives in the water.
Answer:
Osteoclasts are the type of cells which are responsible for the absorption of calcium from bones.
Explanation:
Osteoclasts is special type of cells which is released by parathyroid gland when the blood have low levels of calcium. Osteoclasts absorb calcium from the bones and add this calcium into the blood to increase the calcium level. If calcium is present in very high amount so this calcium is stored in the bones of the body and extracted when needed by the body.
