Question 2
The modern periodic table is based on what?
The right answer is the one marked above.
The atomic number and the electron configuration — the two things sections 3.1 and 3.2 were about.
Not the mass number, which is what several early attempts used before atomic number was understood. Arranging by atomic number is what makes the repeating pattern come out cleanly, because the outer electrons repeat as you count up through Z.