Step 1: Understanding the Question:
The task is to find the phrase that means the same as "platitude".
Step 2: Key Formula or Approach:
Recall where the word is normally used, in conversation about dull, repeated remarks, then match that context against each answer choice.
Step 3: Detailed Explanation:
A platitude is a comment that sounds wise or caring on the surface but has been repeated so many times that it carries no real weight, such as saying "everything happens for a reason" without any thought behind it.
"Condolence" belongs to a different context altogether: it is about comforting someone who is grieving, not about a stale remark.
"Empty promise" refers to a pledge that will not be honored, which is a different failure of speech than being unoriginal.
"An obligation" is a duty, again unrelated to the freshness or staleness of words.
Only "a trite phrase" describes speech that has become dull and predictable from overuse, which is the exact quality a platitude has.
Step 4: Final Answer:
The correct synonym is "a trite phrase", so the answer is option (b).