The mistake in the first sentence is in part C: "wedding." It should be "wedding" instead of "wedding" if the context implies a specific event, but contextually "wedding" is correct as it is. The real mistake is in using "is playing" with "every night," as it implies an ongoing action that may not fit if it refers to a specific event, such as a wedding.

For the second sentence, "6 a.m" should have a period after "a" to correctly style "a.m." as "6 a.m." or "6 AM."

In summary:
1. First sentence: "is playing" may need revision based on context, but "wedding" is correct.
2. Second sentence: "a.m." should have a period after "a."