Explanation: The phrase “which takes effect Monday” adds non-essential information and is correctly enclosed by commas. The colon is appropriate because a complete clause introduces a list of the three changes. The commas within the list then separate its individual items clearly. The distractors omit necessary commas or use a semicolon or comma where a colon is required. For punctuation questions, first identify the sentence’s main clause, then determine whether added information and introduced lists require separate punctuation rules.