---Where is Class       ?

---It’s on the       floor.

Six; third

Sixth; third

Six; three

Sixth; three

考查数词辨析。句意：----六班在哪里？---在三楼。英语中表达序号时，如果用基数词表示：名词+基数词，如六班，Class Six;如果用序数词表示：the+序数词+名词，如三楼，即the third floor。故选A项。

I would really appreciate       if you can make time in your schedules to attend my lecture today.

that

it

this

one

考查形式宾语。句意：如果你今天能从日程安排中抽出时间来听我的讲座的话，我将不胜感激。I would appreciate it if/when...如果/当...时，我将非常感激。it 做形式宾语。故选B项。

It was along the Mississippi River _________ Mark Twain spent much of his childhood.

how

which

that

where

此处构成It was...that...强调句式，句中强调了介词短语along the Mississippi River。故选C。