Explanation

(a)
Zinc, does not react with cold water.
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ Zn + H_{2}O\ \rightarrow ZnO + H_{2}O\ \uparrow$
steam
$\ \ \ \ \ \ \ \ \ \ Zn + 2NaOH\ \ \rightarrow Na_{2}ZnO_{2} + \ H_{2}\ \uparrow$
$\ \ \ \ Zn + 2HCl\ (dil.)\ \rightarrow Zn\ Cl_{2} + \ H_{2}\ \uparrow$
$\ \ Zn + H_{2}SO_{4}\ (dil.)\ \rightarrow ZnSO_{4} + \ H_{2}\ \uparrow$