Final answer:
The correct comma placement in the sentence 'I intended to go to the evening meeting ___ it is scheduled for the same time as the main speaker's presentation.' would be after 'meeting'.
Step-by-step explanation:
The correct comma placement in the sentence would be after 'meeting'. So the correct sentence would be:
'I intended to go to the evening meeting, but it is scheduled for the same time as the main speaker's presentation.'
The comma is placed after 'meeting' to separate the two independent clauses in the sentence. This helps to clarify the meaning of the sentence and make it easier to read.