(a) $Na+{{H}_{2}}O\to NaOH+\frac{1}{2}{{H}_{2}}$

    $2NaOH+CuS{{O}_{4}}\to Cu{{\left( OH \right)}_{2}}\downarrow +N{{a}_{2}}S{{O}_{4}}$

(b) $C{{O}_{2}}+Ca{{\left( OH \right)}_{2}}\to Ca{{\left( HC{{O}_{3}} \right)}_{2}}$

(c) $6NaOH+A{{l}_{2}}{{\left( S{{O}_{4}} \right)}_{3}}\to 3N{{a}_{2}}S{{O}_{4}}+2Al{{\left( OH \right)}_{3}}\downarrow $

     $Al{{\left( OH \right)}_{3}}\downarrow +NaOH\to NaAl{{O}_{2}}+2{{H}_{2}}O$

(d) $3NaOH+FeC{{l}_{3}}\to Fe{{\left( OH \right)}_{3}}\downarrow +3NaCl$

Chỉ có (a) và (d)

=> Đáp án D