Which one the following compounds will readily react with dilute $$\mathrm{NaOH}$$ ?

The shape of carbocation is :

When $$\psi_{\mathrm{A}}$$ and $$\psi_{\mathrm{B}}$$ are the wave functions of atomic orbitals, then $$\sigma^*$$ is represented by :

The emf of cell $$\mathrm{Tl}\left|\underset{(0.001 \mathrm{M})}{\mathrm{Tl}^{+}}\right| \underset{(0.01 \mathrm{M})}{\mathrm{Cu}^{2+}} \mid \mathrm{Cu}$$ is $$0.83 \mathrm{~V}$$ at $$298 \mathrm{~K}$$. It could be increased by :