Here are the errors in each sentence:

1. **Error in A:** "what did happen" should be "what happened" — In indirect questions, the auxiliary verb "did" is not used.

2. **Error in B:** "too much" should be "too many" — "Garlic" is uncountable, but since "bunches" is plural, "too many" is appropriate.

3. **Error in A:** "the breakfast" should be "breakfast" — No article is needed before "breakfast" in this context.

4. **Error in D:** "so slow" should be "so slowly" — The adverb form "slowly" is needed to describe how the train traveled.

5. **Error in C:** "doesn't he?" should be "does he?" — The statement is negative, so the tag question should be positive.

These errors make the sentences grammatically incorrect.