The correct answer is At 00:12, 00:24, and 00:36 each day.

The cron expression is evaluated left to right and the fields are seconds then minutes then hours then day of month then month then day of week then year. The first field is 0 so the job runs at the zero second of the minute. The minutes field is 12,24,36 so it runs at those specific minutes. The hours field is 0 so it runs only during the midnight hour. Putting those parts together yields executions at 00:12, 00:24, and 00:36 each day.

Every 12 seconds continuously throughout the day is incorrect because the seconds field is 0 rather than an interval like */12, so the schedule does not fire every 12 seconds.

At 12 minutes 24 minutes and 36 minutes past every hour of the day is incorrect because the hours field is 0 not a wildcard, so the schedule is limited to the midnight hour and does not run past every hour.

Every 12 minutes during every hour of the day is incorrect because the minutes are a specific list of three values rather than an every 12 minute pattern and the hours value restricts execution to hour 0 only.

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