1.填when.
因为关系副词在从句中作状语.这句不是不是宾语从句.
2.填that（这里也可什么都不填）.
因为关系代词在从句中作宾语,即作spent 的宾语.
是填when或that,要看 关系代词或副词在从句中所做的成分,而与days 或day无关.
3.填where.
关系副词作状语.
4.本句要填which.
填where时,in要省去.因为where=in which
5.如：
（1）This is the place where we met last time.
(2)This is the place which I have been looking for.
My son goes to No.1 Middle School _______ I used to study in.括号里是不是只能填which,是不是如果没有in的话可以填in which或者where呢?
一般情况是这样的.但介词in要根据动词作相应变化