To which of the following four types does this reaction belong: $B^{-} + R - A \to B - R + A^{-}$?

In the given compound,how many sites are available for the attack of $CH_3O^{-}$?

What is heterolytic cleavage of a chemical bond?

What type of fission is possible by sunlight?

Match the reactions in column $I$ with appropriate types of steps/reactive intermediate involved in these reactions as given in column $II$.
| Column $I$ | Column $II$ |
| :--- | :--- |
| $(A)$ $1-$phenylpentane$-1,4-$dione $\xrightarrow{aq. NaOH}$ $3-$phenylcyclopent$-2-$en$-1-$one | $(p)$ Nucleophilic substitution |
| $(B)$ $4-$chloro$-1-$phenylbutan$-1-$one $\xrightarrow{CH_3MgI}$ $2-$methyl$-2-$phenyltetrahydrofuran | $(q)$ Electrophilic substitution |
| $(C)$ $4-$hydroxy$-1-$phenylbutan$-1-$one $\xrightarrow{H_2SO_4}$ $2-$phenyl$-4,5-$dihydrofuran | $(r)$ Dehydration |
| $(D)$ $4-$methyl$-4-$phenylpentan$-1-$ol $\xrightarrow{H_2SO_4}$ $1,1-$dimethyl$-1,2,3,4-$tetrahydronaphthalene | $(s)$ Nucleophilic addition |
| | $(t)$ Carbanion |

The major product in the following reaction is