(1) The intersection point is carbon atom. According to the carbon tetravalent rule, the molecular formula of amantadine is C1H17N, so the answer is: C1H17N;

(2) the amino group is equivalent to 1 h atom, and the unsaturation of C1H17N is 2×1+2? 162=3, the aromatic compound contains at least one benzene ring, and its unsaturation is ≥4, so there is no isomer of the aromatic compound in amantadine, so the answer is: no;

(3) shikimic acid removes 2 molecules of water to generate A, and A contains benzene ring. If one hydrogen atom on the benzene ring is replaced by chlorine atom, two isomers may be generated. The reaction of shikimic acid changing into A is elimination reaction, and p-hydroxybenzoic acid and water are generated. The reaction equation is:,

, so the answer is:; Elimination reaction;

(4) p-hydroxybenzoic acid undergoes polycondensation reaction under certain conditions to generate poly (p-hydroxybenzoic acid methyl ester) and water, so the structural formula of B is:, so the answer is:;

(5) As a homologue with salicylic acid, it should contain 1 phenolic hydroxyl group, 1 carboxyl group and 1 benzene ring, and its molecular composition differs by several CH2 groups.

A contains phenolic hydroxyl group and carboxyl group, and its molecular formula differs by 1 CH2, so A is correct;

B, whose molecular formula differs by 1 CH2, contains carboxyl and alcohol hydroxyl, and has different functional groups, so b is wrong;

C contains phenolic hydroxyl and carboxyl, and the molecular formula differs by 2 CH2, so c is correct;

D, whose molecular formula differs by 1 CH2, contains ester group and phenolic hydroxyl group, and has different functional groups, so D is wrong.

Therefore, the answer is: AC.