(a)
B2O3⟶ oxide of boron (non-metal) :acidic
CaO⟶ oxide of calcium (metal) : basic
(b)
B2O3⟶ oxide of boron (non-metal) : acidic
SiO2⟶ oxide of silicon (non-metal) : acidic
(c)
N2O⟶ oxide of nitrogen (non-metal) : neutral
BaO⟶ oxide of barium (metal) : basic
(d)
CaO⟶ oxide of calcium (metal): basic
SiO2⟶ oxide of silicon (non-metal): acidic
So, option (b) is the correct answer.
B2O3 and
SiO2 are being acidic oxide they react with base to give salt and water.
B2O3+2NaOH⟶| 2NaBO2 |
| Sodium‌metaborate |
+H2O SiO2+2NaOH⟶+H2O