C-07-Q077mediumsingle_mcqFor the sequence with un=1nu_n = \dfrac{1}{n}un=n1, if un<10−8u_n < 10^{-8}un<10−8, the value of nnn satisfies —an<10−8n < 10^{-8}n<10−8bn>108n > 10^{8}n>10