A. 2
B. 3
C. 4
D. 5
A. ${P}_{2}{O}_{5}, {C}{a}{O}, {C}{u}{O}$
B. ${C}{a}{O}, {C}{u}{O}, {B}{a}{O}, {N}{a}_{2}{O}$
C. ${B}{a}{O}, {N}{a}_{2}{O}, {P}_{2}{O}_{3}$
D. ${P}_{2}{O}_{5}, {C}{a}{O}, {P}_{2}{O}_{3}$
A. ${P}_{2}{O}_{5}, {C}{a}{O}, {C}{u}{O}, {B}{a}{O}$
B. ${B}{a}{O}, {S}{O}_{2}, {C}{O}_{2}$
C. $CaO, CuO, BaO$
D. ${S}{O}_{2}, {C}{O}_{2} , {P}_{2}{O}_{5}$
A. CaO, CuO
B. NaO, CaO
C. NaO, SO
D. CuO, SO