he has not seen Fred at the gym for some time.其中是否涉及到什么知识点.
问题描述：
he has not seen Fred at the gym for some time.其中是否涉及到什么知识点.
答
he has not seen Fred at the gym for some time.
现在完成时
他已经有一些日子没在健身房看到Fred了.
for 一段时间,用现在完成时.