Finally,the thief handed everything _____ he had stolen to the police.
A.whichB.whatC.whateverD.that在线课程D
what，whatever不能用作引导定语从句的关系代词，排除B、C。which，that虽均可作为关系代词，指代表示物的先行词，并引起一个定语从句，但要注意，下列场合该用that而不用which：
1)当先行词是all,few,little,much,everything,,something,anything时。
All that we have to do is to practise every day. (that指代先行词all，不用which)
2)当先行词被only,very,same,no,any,some,all,few,little等所修饰时。
This is the very watch that I lost yesterday. (先行词watch由very修饰，不用which)
3)当先行词为序数词或最高级形容词所修饰时。
This is the best film that has been shown these years. (先行词由最高级the best修饰，不用which) 4)当定语从句同时修饰表示人和物的先行词时。
They talked about the school and the teachers that they had visited．
(that同时指代the school与the teacher，不用which)
综上所述，本题先行词为everything，故关系代词只有选that。