==> In the original condition, there is 1 variable (r), and in order to match the number of variables to the number of equations, there must be 1 equation. Since there is 1 for con 1) and 1 for con 2), D is most likely to be the answer.
For con 1), from r2(r-1)=0, you get r=0,1, hence it is not unique and not sufficient.
For con 2), from 2r=0, you get r=0, hence it is unique and sufficient. Therefore, the answer is B.
Answer: B
For con 1), from r2(r-1)=0, you get r=0,1, hence it is not unique and not sufficient.
For con 2), from 2r=0, you get r=0, hence it is unique and sufficient. Therefore, the answer is B.
Answer: B
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