Basic nature of oxides increases with increase in the size of cation. 

The increasing order of cations is: Al³⁺ < Mg²⁺ < Na⁺ < K⁺

Therefore the increasing correct order of basic strength is: Al₂O₃ < MgO < Na₂O < K₂O

Hence, the correct option is (B).

Aryl halides are less reactive towards nucleophilic substitution reaction as compared to alkyl halides due to resonance stabilization. In alkyl halides, the carbon atom is sp³-hybridized whereas, in aryl halides, it is sp²-hybridized and hence, more electronegative.

Hence, the correct option is (B).

As we come down the group atomic size increases, thus bond length decreases, bond strength increases and acidic strength increases and basic strength increases and nucleophiles having different donor atoms in the same group then nucleophilicity is anti-parallel to basic strength. Then order will be- Cl^– < Br^– < I^–

Hence, the correct option is (A).

The solvent affects the rate of reaction because solvents may or may not surround a nucleophile, thus hindering or not hindering its approach to the carbon atom. Polar aprotic solvents, like tetrahydrofuran, are better solvents for this reaction than polar protic solvents because polar protic solvents will hydrogen bond to the nucleophile, hindering it from attacking the carbon with the leaving group. A polar aprotic solvent with a low dielectric constant or a hindered dipole end will favor SN² manner of nucleophilic substitution reaction. Examples: DMSO, DMF, acetone etc. In polar aprotic solvent, nucleophilicity parallels basicity.

Hence, the correct option is (C).

N-acetyl-para-aminophenol(or paracetamol) is an antipyretic which can also be used as Analgesic to relieve pain without addiction and mood modification.

Hence, the correct option is (B).

BF₃ is a Lewis acid due to an incomplete octet of Boron. Among BF ₃ BCl₃,BBr₃ and so on, BF₃ is the weakest Lewis acid due to back bonding of lone pair electron of F to p-orbital of Boron.

B has vacant available p-orbital in BF₃ and hence it involves pπ - pπ back bonding which is not possible in CF₄ as C does not have any vacant orbital.

Hence, the correct option is (D).