The correct choice is Option 3: 'Placing the meeting materials by this evening.' The text states: 'ミーティングですが、明日の午前10時に変更になりました' (The meeting has been changed to tomorrow at 10 AM). Therefore, going to the meeting room today (Option 1) is no longer required. The prompt then asks what to do first/earliest. The written instruction is: '資料は今日の夕方までに私の机の上に置いておいてください' (As for the materials, please place them on my desk by this evening). This is the only active task given to Tanaka with a deadline ('今日の夕方まで' - by this evening), which is earlier than the meeting tomorrow. Thus, Option 3 is correct.