Let $(s_n)_{n\ge1}$ be the sequence defined inductively by setting
$s_1=1$ and $s_{n+1}=\frac{s_n}2+\frac{2}{s_n}$.  You may take it for
granted that this sequence converges.  The limit of the sequence is
\correct 2
\wrong $\sqrt 2$
\wrong 4
\wrong 0
\wrong 1
