Answer:
identify the variables
Explanation:
control:type of lemon used
dependent:whether apple slice turns brown at pH>2
independent:pH value
I'd say that it is incorrect because each carbon atom should bond 4 times and all three carbon atoms in this structural formula only bond once. The reverse is true for hydrogen atoms. They only form one bond but in this structural formula two of them have four bonds. I don't know about nitrogen though.
Answer:
All of the above is the answer.