b............................................
Atomic number.
The atomic number is what defines the element.
In descriptive investigations, we still haven't formed any hypothesis yet so we seek information by asking question.
It's not repeatable because repeating the questions over and over again without any clue about what we want to seek is completely waste of time.
Hope this helps xox :)
Answer:
magnesium + oxygen ----> magnesium oxide
Most of the compounds containing C and H are organic so A. CH4 is the correct option
