[求助]新東方GMAT語法全解

grumpy0317

Any medical test will sometimes fail to detect a condition when it is present and indicate that there is one when there is not.  
(B)when a condition is present and indicate that there is one
(C)a condition when it is present and indicate that it is present
(D)when a condition is present and indicate its presence
(E)the presence of a condition when it is there and indicate its presence

正解为(C) 白勇的解答上说省略结构必须能还原,故ABDE皆不正确,但是正确答案(C)却让我看不太懂,想请版友解释一下此题，多谢