Eugene Cernan was not the last, but he was the most recent.
        
                    
             
        
        
        
Answer:
a. The sheets move toward each other and the gap narrows.
Explanation:
This exercise is related to fluid mechanics, when blowing between the two sheets, we can apply Bernoulli's equation, where the index 2 is the space between the two sheets
        P₁ + ½ ρ g v₁² + ρ g y₁ = P₂ + ½ ρ g v₂² + ρ g y²
if the two leaves are at the same height
                       y₁ = y₂
  whereby
          P₁ + ½ ρ g v₁² = P₂ + ½ ρ v₂²
for the air velocity between the leaves let us use the continuity equation
         A₁ v₁ = A₂ v₂
the area between the leaves is less than the external area, so the air speed must increase. If we use this in Bernoulli's equation, increasing the speed 2 (between the leaves) to maintain equality the pressure must decrease.
If the pressure decreases, the blades should move closer
When resisting the answers, the correct one is  a
 
        
             
        
        
        
Answer:
B, It reacts with oxygen to form a new substance
Explanation:
B
 
        
             
        
        
        
No, you would aim slightly above, because when you throw the spear and it travels through the air it will fall slightly downwards by the time it reaches the fish.