The active site is complementary to its substrate due to its specific 3D structure. The substrate fits in to one specific active site so an enzyme will only bind to one substrate. They are SPECIFIC. Lock and key theory.
        
             
        
        
        
Answer:
Book lungs
Explanation:
The horse shoe crab has a hard outer surface carapace which has the shape of a horse shoe.
It has book lungs which come in 5 sets. The lungs are usually found on the ventral side of the crab.
The book lungs acts as gills which is used in breathing when the horseshoe crab is in water . The book lungs also helps the crab to breathe on land for a certain period of time provided the lungs are moist.
 
        
             
        
        
        
After a tornado or a hurricane the local ecosystem will be very damaged, and when the wind stops blowing, or all the water is drained/dried, the ecosystem will start recovering:
- The earth will recover
- Plants will regrow.
- Animals will come back.
- The ecosystem will slowly rebuild.
Hope it helped,
BiologiaMagister
 
        
                    
             
        
        
        
<h2><u>Full Question:</u></h2>
In the alveolus pictured above, a disease or injury to which structures would reduce the ability of oxygen to diffuse from the alveolar space to the capillary?
A. A and B
B. B and C
C. B and D
D. A and D
<h2><u>Answer:</u></h2>
The correct answer is option D. 
<h3><u>Explanation:</u></h3>
Alveoli is defined as the unicellular thickened sac like structure of lungs which helps in exchange of gases in lungs. The exchange membrane of lungs comprise of three structures -
A. The epithelium cells of Alveoli, 
B. The basement membrane of alveolar epithelium,
C. The endothelial layer of blood capillary.
The red blood cells described here won't cause any problems to the diffusion of gases from alveolar cavity to blood. The structures mentioned here as the type 2 cells of Alveoli which secrete lecithin, a surfactant which releases the surface tension of Alveoli. This compound prevents the Alveoli from collapsing and helps in diffusion of gases. The other structure mentioned here as D are the alveolar epithelium which is the unicellular thickened membrane of Alveoli, helping in gaseous exchange. 
 
        
        
        
Answer: It leads to 4 daughter cells.
I hope this helps.