The rare bird, considered extinct for over fifty years and actually thriving in a remote part of the Andes, has made a remarkable comeback over the past decade.

Meaning :

This sentence puts a contrasting information ... The rare bird was considered extinct for over 50 years .However it was actually thriving in a remote part of Andes . The rare bird has made a remarkable comeback over the past decade .

Analysis :

Two contrasting pieces of information has been connected through 'and' : Error
1. The rare bird considered extinct for over 50 years .
2. It was actually thriving in a remote part of Andes .

In this original choice .
Considered is used as a modifier to rare Bird. Also thriving is a modified to rear Bird. Uses of both the modifier is correct in the sentence


(A) The rare bird, considered extinct for over fifty years and actually thriving in a remote part of the Andes, has made a remarkable comeback over the past decade.

Use of 'and' for the contrasting information is an error as shown in the error analysis.

(B) The rare bird, which had been considered extinct for over fifty years but it was actually thriving in a remote part of the Andes, has made a remarkable comeback over the past decade.

There is no comma before but ,hence use of 'it' is redundant subject ...error... out


(C) The rare bird, which was considered extinct for over fifty years and had actually been thriving in a remote part of the Andes, made a remarkable comeback over the past decade


1.Use of 'and' for the contrasting information is an error as shown in the error analysis. .
2.Use of had is wrong as well .
3. Use of made is changing the meaning because of wrong tense ..


(D) The rare bird was considered extinct for over fifty years, but it was actually thriving in a remote part of the Andes, and, over the past decade, has made a remarkable comeback.

This sentence is correct .
1. The contrast is shown properly .
2.Use of has made also properly conveying the meaning that the effect of comeback is still on.

(E) The rare bird was considered extinct for over fifty years, was actually thriving in a remote part of the Andes, and, over the past decade, has made an remarkable comeback.


1.Use of 'and' for the contrasting information is an error as shown in the error analysis. .
2.There is is a parallelism error in the sentence. Two verb phrases in the list are in past tense and one is in Present perfect tense, creating the parallel error.


Hence D is the best choice and is my answer .