Carbon dioxide is transported in the blood in three ways: (i) dissolved in solution; (ii) buffered with water as carbonic acid; (iii) bound to proteins, particularly haemoglobin. Source: https://academic.oup.com/bjaed/article/5/6/207/331369
The two-layered sac surrounding the heart is the pericardium.
Hope this helps!
DnaG
That’s the first answer that came up on google
The answer is natural selection
