The most stable carbocation among the following is:

Usually, $3^{\circ }$ carbocations and benzyl carbocations are very stable. However, the cyclopropylmethyl carbocation is exceptionally stable. This is due to the "dancing resonance" or overlap of the bent $\sigma$ -orbitals of the cyclopropane ring with the vacant $p$ -orbital of the carbocation. This stabilization is even greater than that provided by resonance in the benzyl carbocation or $+I$ in the $3^{\circ }$ carbocation.