The correct options are
B F
D Cl
Fluorine (F) and chlorine (Cl) have seven electrons in their outermost shell. These seven electrons are bound tightly by their nucleus. Also, as compared to sodium (Na) and magnesium (Mg), F and Cl have a tendency to gain an electron to achieve octet whereas Na and Mg being metals have tendency to lose electrons to gain octet. Hence, it is more difficult for F and Cl to lose an electron as compared to Na and Mg.