The correct answer is a) 6.
Explanation: In Lewis symbols, dots represent the valence electrons of an atom. Oxygen, which is in Group 16 of the periodic table, has a total of 6 valence electrons. This is because it has 8 electrons in total, but 2 are in the first shell, leaving 6 electrons in the second shell. Therefore, when drawing the Lewis symbol for oxygen, you would place 6 dots around the chemical symbol (O) to indicate its valence electrons.