With the emergence of private companies producing weapons

Clearly D.

Will go with D.

D address both points mentioned in the passage.
--> Level of secrecy in private companies
--> and why it would help the country rather than make the country weak

Straight D.

I beg to differ.I'll go with C.
This in turn would decrease the efficiency of each of the research/developer and prevent our country from being number one in weaponry development and production.

The new level of secrecy will not decrease the efficiency of researchers.

This question is VERY similar to the one in the OG about research and development in Pharmaceuticals...

the answer is D

I think that zoom612 understood my logic in this question. And yes, u2lover, that question from the OG inspired me to come up with something similar... So, the correct answer, in my opinion is C.
The tension here is between the leak of information and the level to which people who work in the industry know each other. If there are links between researchers in different companies, then the new level of secrecy would cause these links to break. On the other hand, though, researchers might be inspired by each others' work which could cause some of them build on what others are working on and put some of the companies forward, though unfairly. as an example, imagine several researchers sharing thoughts with each other. this might cause one of them to start a project that someone else has merely dreamt about. the word 'efficiency' in the question stem plays an important role.
a. does not deal with the question stem directly, rather merely mentions an additional fact. we do not know how long it would take for our country to lose its position.
b. so what? we do not know the results. we have to have information in order to draw conclusions.
c. states that there are not many links, if at all, between researchers in different companies. this means that new levels of secrecy would not influence efficiency of the researchers work, as they are not inspired by each other's thoughts.
d. compares local companies with foreign markets, but does not indicate the relationship between the local companies. this answer suggests that most leaks help such companies abroad, giving them an unfair advantage. if the local researchers share their knowledge with each other and therefore boost efficiency, enabling our country to be number one in the field in the world, new levels of secrecy would make it impossible, decreasing efficiency of each individual researcher.
e. if the researchers know everything about each other and their work, then new level of secrecy would definitely decrease efficiency.

Looks like C.

a) doesn't affect the argument in the question stem.
b) strengthens the argument. we are looking for weaken.
c) addresses both the points; it says - (1) the new level of secrecy is not reqd (2) also, since they already don't know the others, efficiency will not be affected even if the new level is introduced.
d) concentrates only on the 'efficiency' part... but not on the level of secrecy. the question mentions both...
e) strengthens the argument. we are looking for weaken.

actually i chosed C at first and edited to D because the passage talks about researches/developers but not about researchers/developer. therefore, i changed my answer to D.

your OA(s) is(are) highly controversial unlike real CR questions and their answers.

completely agree with you MA. I followed the difference between "researches" and "researhers" and chose my answer.