英语：I am afraid that is the most important place( )you should

因为句子前面有了比较级的最高级了,所以只能用that喽!补充：为了你能真的懂什么时候用which,而不能用that,或者只能用that不能用which,下面我给你一个总结过了的：that和which做比较,主要在于它们在定语从句中的用法that 和which在定语从句中都是做关系代词,指代先行词是事物的名词或代词（that还可以指代人,which 不可以）。通常情况下二者可以互换。区别：关系代词用that（不用which）的情况：1。先行词是all,anything,everything,nothing等,关系代词应用thatThat's all that he told me。2。先行词前有the only,the same,the very 或no,little,much,any,every,all 等修饰时,关系代词应用thatShe is the only person that I know in this company。3。先行词前有序数词或形容词最高级修饰时,关系代词常用thatThe first thing that I want to do is to take it away。4。当先行词同时含有"人"或"物"时,关系代词应用that5。在固定结构the same。。。that。。。; so。。。that。。。; such。。。that。。。以及it is/was。。。that。。。的强调句型中,要用thatThis is the same park that we once visited。6。如主句以there be开头时,关系代词应用thatThere is a room that has two windows。关系代词用which（不用that）的情况：1。非限制性定语从句中关系代词一般要用whichShe won the competition,which made the whole family very happy。2。关系代词前如有介词,关系代词须用 which; 如把介词移至句末,可用that(或省略)There’s only one problem about which they disagree。This is the key (that) she was looking for。3。如果先行词是that,关系代词应用 whichI know that which you told me。4。如先行词和定语从句之间被其它较长的成分分隔,常用whichLarry told her the story of the young airman which I narrated at the beginning of this book。(先行词为story)5。在"those+复数形式的名词"结构中,其后的关系代词多用whichA shop should keep a stock of those goods which sell best。6。一个句子中如有两个定语从句,第一个定语从句用了关系代词that,第二个从句中的关系代词宜用which;但在平行结构中,应重复同一个关系代词This is the book that you bought which you have lost。I have a house which is located on the hillside,which faces the south。此外,that还可引导同位语从句,which不能I have heard the news that they had won the game。