Because science is always changing and every time you cam come up with a new outcome.
        
             
        
        
        
Answer:
a
. Fish need 10 ml of water purifier to survive.
Explanation:
Fish need 10 ml of water purifier to survive because the data of 10 ml and 20 ml purifier is the same so it is recommended to use 10 ml purifier. First the data was same but by recording next week data, it shows slightly increase in the value of tank 2 while in the last week, both has the same value so we can concluded that by using 10 ml purifier is enough for the fish to survive.
 
        
             
        
        
        
Answer:
Laws of stratigraphy help scientists determine the relative ages of rocks. This law states that deeper rock layers are older than layers closer to the surface. An unconformity is a gap in rock layers. They occur where older rock layers eroded completely before new rock layers were deposited.
Explanation:
The study of rock strata is called stratigraphy. The laws of stratigraphy can help scientists understand Earth’s past. The laws of stratigraphy are usually credited to a geologist from Denmark named Nicolas Steno. He lived in the 1600s. 
Hope this helps!
Brain-List?
 
        
             
        
        
        
I just had this answer but it hasn't been graded. I put 1. Meteor impacts, 2. volcanic gases and 5. Milankovitch cycles. I didn't put earthquakes because I wouldn't think it would affect the climate changing since they just affect ground movement.
        
                    
             
        
        
        
Answer:
30% Thymine
Explanation:
If 30% of Adenine is present, it would be reasonable to assume that 30% of Thymine will be present, as the ratio between the two complementary nitrogenous bases will be roughly equal.
Therefore, that leaves us with 40% between Cytosine and Guanine. Since the ratio between them would be equal, it gives us 20% of Cytosine and 20% of Guanine.
<u>Therefore:</u>
30% of A + 30% of T + 20% of C + 20% of G = 100% DNA