How do merge sorts work?

Question $5$ options:

Each item in the list is individually compared with the following item starting with the first value till the last.

Each item in the list is compared with the following item starting with the last value till the first.

Taking one item at a time from an unsorted list, each new item is compared with the previous until its place is found.

They split the list to single elements before piecing them back together, one sublist at a time.