I. Structural formula of borax (Na2B4O7⋅10H2O) is Na2[B4O5(OH)4]⋅8H2O⇒ correct statement. II. Aqueous solution of borax is basic in nature, because borax in water dissociates into H3BO3 (weak acid) and NaOH (strong base). Na2B4O7+7H2O⟶4H3BO3+2NaOH⇒ Incorrect statement. III. Cobalt (Co) gives blue colour of cobalt metaborate [Co(BO2)2] in borax bead (NaBO2+B2O3) test ⇒ Correct statement. So, the correct statements are (I) and (III).