Answer:
The correct option is: c. in blood
Explanation:
A kidney is a bean-shaped organ, that is present below rib cage in the retroperitoneal space. In vertebrates, the kidneys are present in pair. Each kidney receives blood from the paired renal arteries. The main function of a kidney is to filter the urea present in the blood with the help of filtering units, called the nephrons.
 
        
             
        
        
        
Answer:
C
new combinations means variations, and the more the variations there is of a species, the more diverse they are
 
        
             
        
        
        
Answer:
D. an educated guess or tentative explanation for a natural phenomenon.
Explanation:
A hypothesis is an idea or explanation that is tested through study and experimentation. Outside science, a theory or guess can also be called a hypothesis. In other words, hypothesis is defined as a proposed explanation for a phenomenon. 
A trial solution to a problem as a hypothesis is often called an educated guess because it provides a suggested outcome based on the evidence.