There                   in the world              China is a great country with a long history and rich culture.

are no doubt; that 

are not doubts; if

is no doubt; that

is not doubt; if

考查固定句型和同位语从句。句意：毫无疑问，中国是世界上有着悠久历史，丰富文化的一个大国。分析句子可知，这个句型为 there is no doubt that 引导，表示“毫无疑问......”.本句为that that 引导的同位语从句，句意和句子结构完整。故选C项。

What some people regard as a         is seen as a plus by many others.

duty

drawback

failure

faith

考查名词词义辨析。句意：一些人认为是一个缺点，而其他许多人则认为这是一个优点。A.duty责任；B.drawback缺点； C. failure 失败；D. faith信念。根据空后plus“优点”可知，空处需用drawback“缺点”与之对应。故选B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。