Answer:
<em>Test group is a group that is modified or </em><em>changed by the researcher </em><em>and is then compared to the </em><em>experimental group while carrying out an experiment. </em>
Explanation:
While observing the data of the test group, it has to be compared with the control group to see if there is any effect of the treatment on the test or not. The control can be positive or negative or both to which the test group is compared. 
 
        
             
        
        
        
Answer:
C. a decrease in the chromosome number in every generation.
Explanation:
hope it helps .
 
        
             
        
        
        
Answer:
probability of the child having attached earlobes since it is recessive i.e (yy)
=1/4
=0.25 × 100%
=25%
Explanation:
 If two heterozygous individuals have a child
i.e let the heterozygous individuals be  = Xy
if both traits crosses together; their F₁ offspring will be;  (XX, Xy, Xy, yy)
 Xy  ×    Xy
           X             y
X        XX          Xy
y        Xy            yy
probability of the child having attached earlobes since it is recessive i.e (yy)
=1/4
=0.25 × 100%
=25%
 
        
             
        
        
        
Answer:
A.The hole in the ozone layer
Explanation:
• Montreal protocol is an international treaty that was signed to control the use of substances that are resulting in the depletion of the ozone hole. 
This treaty was signed in the year 1987 and became effective form 1989.
• Since the time that this treaty has come into force, there has been a significant improvement in the ozone hole that was observed over Antarctic as it's size has decreased. 
• This improvement has been possible because the treaty helped to phase out chemicals such as chlorofluorocarbons, carbon tetrachloride, etc. that are responsible for ozone hole depletion.