Answer:
A - 3:1
Explanation:
In order to determine what number of offspring will have attached earlobes, we must make a Punnett table. We know that attached earlobes are the dominant gene, and we know unattached earlobes are recessive. 
 | P | p
——————-
P | PP | Pp |
——————-
p | Pp | pp |
As we can see, only one out of the four squares has two recessive genes. Therefore, our answer would be A - 3:1.
 
        
                    
             
        
        
        
There is a valve at the meeting point between each ureter and the bladder prevents the back flow of urine from the urinary bladder to the kidney
        
             
        
        
        
Answer: Y represents carbon and z is oxygen which gives CO2
Explanation: To photosynthesis to occur Carbon has to reacts with oxygen to give carbondioxide (Co2) which then combines with hydrogen (H2) and oxygen to give water (H20) the reaction gives glucose (C6H12O6).
Equation for photosynthesis = 6CO2+6H20- C6H12O6
 
        
             
        
        
        
i believe the answer is Abrasion and Impact. Hope this helps :-)
 
        
             
        
        
        
An example of something that does not have mass would most likely be air.  Because in order for something to have mass, it must take up space and have shape.  Anything that you can think of that does <u>not</u> have <u>space or shape</u> does not have mass.