Why is the Wurtz reaction not preferred for the preparation of alkanes containing an odd number of carbon atoms?

A hydrocarbon C₅H₁₀ does not react with chlorine in the dark but gives a single monochloro compound C₅H₉Cl in bright sunlight. Hydrocarbon could be:

The above-mentioned compounds that react faster in S N₂ reaction with OH^- from each given pair respectively are:
1. CH₃Br, CH₃I
2. CH₃Br, (CH₃)₃CCl
3. CH₃I, CH₃Cl
4. CH₃I, (CH₃)₃CCl

Primary alkyl halide C₄H₉Br(A) reacted with alcoholic KOH to give compound (B). Compound (B) is reacted with HBr to give (C), and it was found that C is an isomer of (A).
(A) with sodium metal, gives compound (D), C₈H₁₈ 
which is different from the compound formed when n-butyl bromide is reacted with sodium.
Compound (A) is :

1. 2-Methylpropene

2. Isobutyl bromide

3. 2,5-Dimethylhexane

4. 2-Bromo-2-methylpropane

The reaction of alkyl chlorides with aqueous KOH and alcoholic KOH is an example of, respectively:

1. Substitution & Elimination

2. Elimination & Substitution

3. Both are Elimination

4. Both are substitution