Her happy look --- that she has done well in the...

Seem
1.与 it 连用,看来好像
It seems that you don't likethis plan.
2.与人称代词连用感到好象,觉得似乎
He seems to be gloomy.
Appear 与 seem 基本相同；
这两个词在语法上就有问题,没有上句的这种用法.
Present 做 呈现、显示 意时的确切意思是
To offer for observation,examination,or consideration; show or display
与此处的语境不符.
Reflect 的一个意思是
To manifest as a result of one's actions
如 A reflect B,即 A 是作为 B 的结果显示出来的.
这与上句的语境比较契合,即她看上去很开心（A）,是因为她考试表现不错(B)
因此答案应该是 B