Answer:
The best way to revise the sentence is the following one:
B) change “mortifying” to “mortified”.
Explanation:
Since the writer was abashed by the harsh criticism, it was only natural that he felt "mortified" rather than "mortifying". Both are adjectives, with different meanings, though.
Adjectives that end with the suffix "ed" express how someone is feeling due to a number of reasons, among them something that was done to them. It is the case here, since the writer suffered the impact of the harsh criticism: it made him feel "mortified". More examples:
The tired man decided to take a rest.
The abandoned place seemed to be ancient.
The desired woman looked bashful.
The respected novelist won an award.
Adjectives that end with the suffix "ing" express the impact someone or something has on others. Examples:
We watched a boring movie yesterday.
The teacher answered the question in a clarifying way.
Mary has a routine of tiring workout.
Terminator is a killing machine.
