Bunuel wrote:
Embryonic stem cell research,
a field many researchers believe that is capable of revolutionizing medicine by treatments that develop the regeneration of human tissue, has been controversial in the United States because of ethical and religious questions arising from the destruction of human embryos.
A. a field many researchers believe that is capable of revolutionizing medicine by treatments that develop the regeneration of human tissue
B. which many researchers believe is capable for revolutionizing medicine by developing treatments for regenerating human tissue
C. a field that many researchers believe is capable of revolutionizing medicine through the development of treatments based on the regeneration of human tissue
D. which many researchers believe is capable to revolutionize medicine based on developing treatments of human tissue regeneration
E. a field that most researchers believe has the capability of revolutionizing medicine that is based on developing treatments of human tissue by regeneration
OFFICIAL EXPLANATION
Embryonic stem cell research, a field many researchers believe that is capable of revolutionizing medicine by treatments that develop the regeneration of human tissue, has been controversial in the United States because of ethical and religious questions arising from the destruction of human embryos.A. a field many researchers believe that is capable of revolutionizing medicine by treatments that develop the regeneration of human tissue
Incorrect.
This answer choice is grammatically incorrect. The use of that in the phrase a field many researches believe that is capable [...] is incorrect.
That can either begin a standard new clause, e.g. believe that [clause] -OR- a relative clause, but not both:
Correct: Researches believe that this field is capable of ...
Correct: Embryonic stem cell research, a field that is capable of ...
Incorrect: Embryonic stem cell research, a field many researches believe that is capable of ...
Note that the difference between a standard and a relative clause is that a relative clause starting with that has no subject -- the subject is what that refers to. Believe that should be followed by a standard clause and begin with a subject.
In addition, the phrase revolutionizing medicine by treatments is illogical: it sounds as if medicine will be revolutionized by the medicine itself receiving treatments, rather than by developing new treatments.B. which many researchers believe is capable for revolutionizing medicine by developing treatments for regenerating human tissue
Incorrect.
While this answer choice corrects the original Relative Clause mistake, it is still grammatically incorrect and illogical. First, the phrase is capable for is incorrect. The correct idiom is to be capable of. Second, the phrase treatments for regenerating human tissue illogically implies that regenerating human tissue is a disease or condition that needs treatment, instead of implying that regenerating human tissue is the method of treatment.C. a field that many researchers believe is capable of revolutionizing medicine through the development of treatments based on the regeneration of human tissue
This answer choice corrects the Relative Clause mistake in the original question, by removing the word that from the phrase many researchers believe (that) is capable.
That can either begin a standard new clause, e.g. believe that [clause] -OR- a relative clause, but not both:
Correct: Researches believe that this field is capable of ...
Correct: Embryonic stem cell research, a field that is capable of ...
Incorrect: Embryonic stem cell research, a field many researches believe that is capable of ...
Note that the difference between a standard and a relative clause is that a relative clause starting with that has no subject -- the subject is what that refers to. Believe that should be followed by a standard clause and begin with a subject.
In addition, this answer choice corrects the logical flaw in the original sentence by clarifying its meaning. Although this answer choice is longer and more wordy, it is the only one which states clearly that medicine will be revolutionized by developing treatments are based on regeneration of tissue.D. which many researchers believe is capable to revolutionize medicine based on developing treatments of human tissue regeneration
Incorrect.
While this answer choice corrects the original Relative Clause mistake, it is still grammatically incorrect. The correct idiom is to be capable of but this answer choice uses is capable to.
In addition, this answer choice changes the meaning of the original sentence. The phrase medicine based on developing treatments [..] limits the revolution only to medicine that is based on such treatments, but the original sentence referred to revolutionizing medicine as a whole i.e. the entire field of medicine.E. a field that most researchers believe has the capability of revolutionizing medicine that is based on developing treatments of human tissue by regeneration
Incorrect.
While this answer choice corrects the original Relative Clause mistake, it changes the meaning of the original sentence. The phrase medicine that is based on developing treatments [..] limits the revolution only to medicine that is based on such treatments, but the original sentence referred to revolutionizing medicine as a whole i.e. the entire field of medicine.