This is ______I wanted.A the one what B which C one which D the one

1.D the one
完整的是 This is the one that I wanted
先行词是the one 后面是由that 引导的定语从句,修饰the one
而that在定语从句中,是充当want的宾语,是宾语成分,可以省略掉,所以就变成 this is the one I wanted
如果用A,应该是 This is what I wanted.what引导的一个表语从句
5.B /
as we know,I think,to be honest 等很多词组都是插入语,它们对原来的句子没有影响
这里as we know是插入语,可以把它忽略掉,那剩下的就是 Oxford is one of the best.这是一个完整句子了.