Being a few minutes late指的是人，跟後面的reason不對稱。另外妳說的對，Being..可以做動名詞，但是指代要清晰.如果要選D,正確地說法是: Being a few minutes late，she should not be dismissed.
(就像妳在朗文上看到的例子:Being a quiet sort of person, I didn't want to get involved.壹樣)
選C是因為 The fact(that...)與reason匹配.
在英語語法裏，句子的對稱性很重要，尤其在GMAT考試中能體現出來.
希望可以幫到妳 謝謝