The options provided in the question are: 1) Bird flu causing viral strains; 2) Computer applications; 3) Supercomputers; and 4) Unmanned aircraft for espionage.
Option 1: Bird flu causing viral strains. This option is incorrect as Eka, Cray XT5, Nebulae, and SAGA-220 are not related to bird flu or any viral strains.
Option 2: Computer applications. This option is also incorrect. While Eka, Cray XT5, Nebulae, and SAGA-220 are computer-related, they are not applications but rather specific types of computer systems or technologies.
Option 3: Supercomputers. This is the correct answer. Eka, Cray XT5, Nebulae, and SAGA-220 are all examples of supercomputers. Supercomputers are high-performance machines designed to handle complex calculations and solve problems at a scale beyond the capabilities of regular computers.
Option 4: Unmanned aircraft for espionage. This option is incorrect as Eka, Cray XT5, Nebulae, and SAGA-220 have no relation to unmanned aircraft or espionage.
In summary, the correct answer is option