Why are alkali metals kept in kerosene oil?

Why is hydrogen kept in the metal activity series?

From the metals : copper, iron, magnesium, sodium and zinc, select a different metal in each case which :

(a) does not react with dilute hydrochloric acid,

(b) can form 2+ and 3+ ions,

(c) arrange the above metals in the decreasing order of reactivity.

Which metal occurs as :

(a) a sulphide,

(b) a halide,

(c) a carbonate,

(d) an oxide.

Also give the names of their respective ores.