DNA methylation is a process by which methyl groups are added to the DNA molecule. Methylation can change the activity of a DNA segment without changing the sequence. When located in a gene promoter, DNA methylation typically acts to repress gene transcription.
The cellular respiration happens in the mitochondria. During the cellular respiration, glucose and oxygen are the reactants during this process and the main product of this process is ATP, with waste products carbon dioxide and water. Therefore, the correct answer would be option B. O2 (oxygen) and C6H1206 (glucose).
A BMI of 18.88 would be pretty normal for a 13 year old if not a bit on the lower side already. Usually we consider a BMI between around 18/19 and around 25 to be that of a normal weight person. If it is below theis, we would recommend to eat more, if ti above this we would recommend to eat less. Considering that we're talking about a 13 year old, perhaps it would be better if he/she ate a bit more to supply his body with the necessary nutritional needs.