Please help me with this

The first and the last one

Explanation:

For the second square, on the bottom right it says it's DD, but that can't be it because the outer things I forgot what they're called, the things outside the square are D and d. If it were to be DD the letters on the outside of the square would have to be DD, not Dd.

For the thirds square, it's the same problem but for the upper right hand square.

where in your body is there an enzyme that does function at a high or low ph? what is the name of that enzyme and its function?