a - 4
b - 2
c --3
d - 1
Explanation:
The 12th Amendment made a foundation change in the process of the elections of the President and Vice President to make it more democratic and to have more people have a say in it.
The 20th amendment finalized the term dates of Presidents and their cabinets and had laws for when there was no clear winner at the ballot.
The 23rd amendment happened due to common demand and allowed DC voters on the poll
The 25th amendment came out of the tragic necessity after John F Kennedy's assassination.