Among alkali metals,lithium is the strongest reducing agent. Which of the following factors is responsible for this?

Choose the alkali metal with the highest reactivity among the following.

Which of the following is the reason why sodium metal conducts electricity?

Given below are two statements,one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: The alkali metals and their salts impart characteristic colour to reducing flame.
Reason $R$: Alkali metals can be detected using flame tests.
In the light of the above statements,choose the most appropriate answer from the options given below.

The electronic configuration of a metal $M$ is $1s^2, 2s^2 2p^6, 3s^1$. The formula of its oxide will be

Which of the following are the by-products in the Solvay process for the manufacture of $Na_2CO_3$?