Answer:
Fish
Explanation:
Fish are vertebrates and only have a single loop-circulation system.
Answer: Option B.
Explanation:
The first experiment of the passage shows that treatment with TGFBR1 and TGFBR2 antagonists led to lower levels of epithelial cell production. For this conclusion to be strongly valid, we want to show a positive correlation between TGFBR activity and epithelial proliferation.
We are wearing masks so we are breathing in CO2 which is not good for us. We are meant to breathe in oxygen and breathe out co2
