Answer: Carbon Monoxide is a very harmful and toxic gas which is formed from incomplete combustion of carbon.
Explanation: red blood cells contain haemoglobin ,which are responsible for carrying oxygen into our body system. So oxygen combines with haemagoblin to form oxyhaemogoblin in the red blood cells .
so if a person starts to intake cigarettes which contain high amounts of carbon monoxide ,it reduces oxyhaemogoblin formation because it binds very tightly to the haemogoblin .then carboxyhaemogoblin is formed and its permanent so causing reduction in aerobic respiration, and reduction in oxygen transport and causing damages to heart muscles.
Hope this helps if you need any more explanation feel free to comment in the comment section below !!!
 
        
             
        
        
        
If a scientist is planning to carry out such an experiment it wouldn't be appropriate to go and test this right ahead without any serious protection. It is always advised that scientists first collect data after they've created their initial hypotheses and read the required literature.
        
             
        
        
        
Answer: A. Average rainfall has decreased 
Explanation:
I might be wrong. sorry if i'm wrong 
 
        
             
        
        
        
The answer would be D, evolved from a common ancestor 
Hope this helps!