0a) The first step to find the major product under the influence of base and thermal conditions is to first identify from where the bond has the maximum possibility to break owing to various factors:
1. Acidity,
2. Unstability,
3. Electronegativity, etc.
b) Then find the possibilities of rearrangements if possible for greater stability.
c) And then finally see and solve to get the greatest possible stable product ,if any.
- a ring formation, a conjuagated system or witnessing resonance .
An example is shown below:
The base first attacks and chlorine being electronegative is eliminated out.
After that rearrangement takes place in order to achieve stability. 
hence a) is the answer.
