Yes a mixture can be made up of only elements and no compounds because you can have gold, nickel and palladium or platinum to form white gold
Allergies (3) because they are the only disorder listed that is a result of the environment.
The characteristics that apply only to prokaryotes from the list given above would be as follows:
-These cells have DNA in a region called the nucleoid.
-Some of these cells have structures like flagella and microvilli.
-These cells have cell walls made of polypeptides and polysaccharides.
Hope this answers the question. Have a nice day.