1.填“that”.因为在后面的句子中只缺宾语,即挂断电话为“hang up the misterious phone”,并没有缺地点的意思,所以用that,不用where.
2判断的依据主要看后面的句子缺不缺成分以及要了解句意.定语从句会缺一些成分,像是主语、宾语、表语等.例如：It is a beautiful school that has a number of students..而同位语从句中不缺成分,从句意上来看,同位语从句是用来解释说明前面的名词,例如：There is a new report that the global temperature is rising.