Transformations of aromatic compounds give the stated major product?

(A) Correct. Friedel-Crafts acylation gives acetophenone, which the Clemmensen reduction converts to ethylbenzene; acylation is used because direct alkylation with ethyl halide could rearrange or poly-alkylate. (B) Incorrect. The strongly deactivating $\mathrm{-NO_2}$ group makes nitrobenzene unreactive in Friedel-Crafts alkylation, and the $\mathrm{AlCl_3}$ also complexes with it. (C) Incorrect. In strongly acidic medium aniline is protonated to the anilinium ion, a meta director, so a large amount of $m$-nitroaniline is formed together with oxidation products; the product is not exclusively para. (D) Incorrect. In the Reimer-Tiemann reaction the electrophilic dichlorocarbene attacks the ortho position of the phenoxide, so salicylaldehyde is the major product and the para isomer is minor.