定期交换信件

exchange letters───交换信件

exercise regularly───定期锻炼；定期运动

The writers, often parents or working people, exchange letters with their teachers regularly, and then come in to Bennington for a few days twice a year.───的作家一般都是身为父母或是已经工作的人，他们定期与他们的教师通信，而且一年两次他们来到本宁顿呆一段日子。