Which of the following statements is equivalent to the assertion $\lim _{n \rightarrow \infty} a_{n}=L ?$ Explain.
$$
\begin{array}{l}{\text { (a) For every } \epsilon>0, \text { the interval }(L-\epsilon, L+\epsilon) \text { contains at least one }} \\ {\text { element of the sequence }\left\{a_{n}\right\} .} \\ {\text { (b) For every } \epsilon>0, \text { the interval }(L-\epsilon, L+\epsilon) \text { contains all but at }} \\ {\text { most finitely many elements of the sequence }\left\{a_{n}\right\} .}\end{array}
$$