The most stable carbocation among the following is:

Which of the following groups as $X$ will decrease the $pKa$ value of the given compound?

Which of the following groups exhibits $(+)R$ effect?

The structure of triphenylmethyl cation is given below. This is very stable and some of its salts can be stored for months. Explain the cause of high stability of this cation.

Given below are two statements,one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$ : Order of acidic nature of the following compounds is $A > B > C$.
(Image shows: $A$ is $2$-chlorocyclohexanol,$B$ is $4$-fluorocyclohexanol,$C$ is $3$-methylcyclohexanol)
Reason $R$ : Fluoro is a stronger electron withdrawing group than Chloro group.
In the light of the above statements,choose the correct answer from the options given below:

Which of the following can show $+M$ or $+R$ effect?