Solution :
$${\left( {C{H_3}} \right)_3}{C^ + }$$ is more stable than $$C{H_3}\mathop C\limits^ + HC{H_3}.$$ Rest all are primary carbo cations hence less stable.
Releted MCQ Question on Organic Chemistry >> General Organic Chemistry
Releted Question 1
The bond order of individual carbon-carbon bonds in
benzene is