Typically you use experimental and control groups in an experiment. a control group is like the default, and the experimental is the one you actually experiment with.
for example if i run an experiment on the effects of food dye on a leaf stem, i’ll have my control group (the ones without food dye) to compare to the experimental group (the ones with food dye) 
the control group is a way for scientists to see how an experiment truly affected or altered the subject
        
             
        
        
        
1-
First, i m going to explain how the disease is inherited.
Like it says in the question, hemophilia's gene is carried on the X chromosome and is recessive.
Females inherit two X chromosomes, one from each parent. They are: XX
Males inherit one X chromosome from their mother and a Y chromosome from their father. They are XY.
I'll represent with Xᵃ- when the chromosome has the disease's gene and with only an X when that chromosome is normal.
2- 
If Joe has hemophilia is because the X chromosome that was inherited from the mother, came with the disease. Since men only have one X chromosome, the gene will be expressed.
However, this doesn't mean that the mother had the disease, she could be only a carrier with this genotype: XᵃX
(there is not enough information to be sure which one is she)
The answers:
3-
Maternal grandmother- COULD HAVE INHERITED
Like i said before, Joe's mother had a least one X chromosome with the disease's gene, and that came from either her father or her mother( joe's Maternal grandmother).
If it came from the grandfather, that means that he was hemophilic.
If it came from the grandmother, that means that she was a carrier or also had the disease. There is not enough info to be sure which genotype she has but either way, there is a possibility.
4-
Maternal grandfather- COULD HAVE INHERITED
Joe's mother had a least one X chromosome with the disease's gene, and that came from either her father( maternal grandfather) or her mother.
If it came from the grandfather, we can be certain he was hemophilic.He had the same genotype as joe which is: Xᵃ Y
5-
Paternal Grandmother and Paternal Grandfather- COULD NOT HAVE INHERITED.
In x-linked recessive diseases, fathers cannot pass it on to their son because they will pass the Y chromosome, not the X.
Joe's father gave Joe the Y chromosome and will not pass any X.
So, even if Joe's father and his side of the family had hemophilia, that wouldn't matter because either way, Joe will not be receiving any X chromosomes. 
        
             
        
        
        
Answer:
definition: one of the three primary embryonic cell layers. 
 
        
             
        
        
        
Glucose is the fuel that feeds your body’s cells, but to enter your cells it needs a key. Insulin is that key.
People with type 1 diabetes don’t produce insulin. You can think of it as not having a key.
People with type 2 diabetes don’t respond to insulin as well as they should and later in the disease often don’t make enough insulin. You can think of this as having a broken key.
Hope this helps!
~Mia