You're changing the test format here from multiple choice.
If your point is that "multiple choice is bad/written answer good", that's a very general hypothesis in the realm of education; it's not fair to be imposing that on this particular test designer in this particular situation who has chosen to deploy the multiple choice method.
I don't see trendy concepts in the original question. Perhaps the mention of scalability qualifies as trendy in distractor A?
Here is the list of externally referencing noun phrases from the question:
"idempotence", "API design", "rise of distributed systems", "large-scale application", "unreliability of networks", "developers", "robust API", "retry attempt", "designing database schemas", "clients", "multiple, duplicate API requests".
Which of these load the question with trendy concepts? API design, distributed systems, large-scale applications, developers, and duplicate requests existed three decades ago or more.