当事件需要在当前时间过后20秒执行，则该时间的“ON SHCEDULE”表达式为（） A: ON SCHEDULE 20 SECOND B: ON SCHEDULE AT 20 SECOND C: ON SCHEDULE AT CURRENT_TIMESTAMP +20 SECOND D: ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 20 SECOND
当事件需要在当前时间过后20秒执行，则该时间的“ON SHCEDULE”表达式为（） A: ON SCHEDULE 20 SECOND B: ON SCHEDULE AT 20 SECOND C: ON SCHEDULE AT CURRENT_TIMESTAMP +20 SECOND D: ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 20 SECOND
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