Study the reaction scheme below and answer the questions which follow. (i) Give the reagents and reaction conditions for the steps represented by i to iv. (ii) Give the structures of compounds A to D.

6. (a) Study the reaction scheme below and answer the questions which follow.

(i) Give the reagents and reaction conditions for the steps represented by i to iv.

Step	Reagent(s)	Reaction conditions
i	Alcoholic KOH	Heat (reflux)
ii	HBr	Room temperature
iii	Aqueous KOH	Heat (reflux)
iv	HCl	Room temperature

(ii) Give the structures of compounds A to D.

Based on the reaction scheme:

• Compound D is explicitly given as CH$_3$(CH$_2$)$_3$OH (1-butanol).
• Step iii is the conversion of A (C$_4$H$_9$Br) to D (1-butanol). This is a nucleophilic substitution where Br is replaced by OH. Therefore, A must be 1-bromobutane.
• Step i is the conversion of A (1-bromobutane) to B (C$_4$H$_8$). This is an elimination reaction, forming an alkene. Thus, B is but-1-ene.
• Step ii is the conversion of B (but-1-ene) to C (C$_4$H$_9$Br). This is the addition of HBr to an alkene. According to Markovnikov's rule, the major product is 2-bromobutane.

A: $\boxed{\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{Br}}$ (1-bromobutane)
B: $\boxed{\text{CH}_3\text{CH}_2\text{CH}=\text{CH}_2}$ (But-1-ene)
C: $\boxed{\text{CH}_3\text{CH}_2\text{CH(Br)}\text{CH}_3}$ (2-bromobutane)
D: $\boxed{CH_3CH_2CH_2\text