"To preform specific useful computing tasks, like word processing and calculation" is the correct answer. This is the whole purpose of system software. The third answer is some other type of software(third party software?) and the fourth answer is most likely a compiler. Those are the easiest to take off. The second could also work.
The two answers I would go with are the first and the second.
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Imagined Risks are simply 'imaginary' risks that are created out of doubt/fear.
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