Consider a sequence $( u _ { n } )$ such that, for every natural integer, we have: $$1 + \left( \frac { 1 } { 4 } \right) ^ { n } \leqslant u _ { n } \leqslant 2 - \frac { n } { n + 1 }$$ We can affirm that the sequence $\left( u _ { n } \right)$: a. converges to $2$; b. converges to $1$; c. diverges to $+ \infty$; d. has no limit.