1、用于一般现在时： I go to school every go to the cinema twice a have our meals three times a scentist explores volcano every two weeks.
He jogs twice a day.
他现在一天慢跑一次。
2、用于一般过去时：
He jogged twice a day.
他当时一天慢跑两次。
3、用于一般将来时：
He will jog twice a day.
4、用于现在完成时：
He has been there twice.
