Which among the following alkali metal elements is used as a coolant in fast breeder nuclear reactors?

Select the incorrect statement.

Given below are two statements:
Statement $I$ : The $4f$ and $5f$-series of elements are placed separately in the Periodic table to preserve the principle of classification.
Statement $II$ : $S$-block elements can be found in pure form in nature.
In the light of the above statements,choose the most appropriate answer from the options given below :

$NaOH$ is prepared by which of the following methods?

By using which process, sodium carbonate is generally prepared?

Which metals upon heating in the presence of air followed by hydrolysis give ammonia?