zài / shù / xué / kè / shàng / lǎo / shī / yòng / jí / hé / de / lì / zi / jiǎng / jiě / bì / bāo / de / gài / niàn在数学课上,老师用集合的例子讲解闭包的概念。In math class, the teacher used sets to explain the concept of closure.