gauravgundal wrote:Reactivating previous post

Mars (Fill in): It is theoretically possible that bacteria developed on Mars early in its history and that some were carried to Earth by a meteorite. However, strains of bacteria from different planets would probably have substantial differences in protein structure that would persist over time, and no two bacterial strains on Earth are different enough to have arisen on different planets. So______________________________________________.
(What would be the best option to complete the passage?)
A. Whether or not bacteria actually developed on Mars.
B. Its likely it is that Martian bacteria were transported from Earth.
C. Martian bacteria could have been carried to Earth by means other than meteorites.
D. All bacteria now on Earth could have arisen from transported Martian bacteria.
E. There could have been strains of bacteria that originated on Earth and later died out

please explain the reason for your answer.

Last sentence should be filled by a sentence which proves that there is only one type of bacteria exists on Earth which is either developed in earth or transported from Mars.
So D fits the bill

Assumption Q ?
Premise : Protein structure of extra terrestial bacteria will probably remain unique based on its origin.
Conclusion : No 2 bacteria have marked difference so the origin has to be unique.
Possible Assumptions :
(A) Valid question. But the overiding query is whether there is a single origin in the first place, then comes the Q of origin. Notice the passage starts by saying theoratically possible.
(B) Already stated, asumptions are unstated.
(C)Discussion is about origin. Mode of transportation does not alter the content.
(D) All are from Mars so there is no difference. Correct assumption.
(E) Likely but the extinct strain cannot have influence on the present lot as the protein strain remains unique. In fact strengthens the ET origin issue.

IMO D

"so" is a conclusion indicator. We need to fill a statement that is within the info given in the stimulus. Remember for inference type questions, you do not need to add additional information. our answer should lie in sync with just what is given in the stimulus.

A. Whether or not bacteria actually developed on Mars. [This is not even a final statement. can you ever end a statement saying whether or not? you need to give a proper conclusion which makes sense]

B. Its likely it is that Martian bacteria were transported from Earth. [this talks about the possibility, but our stimulus tells that incase bacteria were transported from mars,then there will be a difference in the strains of bacteria, but no such difference is visible. Eliminated!]

C. Martian bacteria could have been carried to Earth by means other than meteorites. [Are we concluding about how they came to earth? our conclusion needs to deal with whether the bacteria at earth originated at Mars or not. Eliminated!]

D. All bacteria now on Earth could have arisen from transported Martian bacteria. [Bingo! now this satisfies the whole stimulus. If all bacteria on earth originated at mars then how will there be discernable difference? they will all be the same in terms of protein structures.]

E. There could have been strains of bacteria that originated on Earth and later died out [does this say whether bacteria originated on Mars and transported to earth or originated at earth? Eliminated!]

Hope this helps!