2. Given the three sides of an obtuse triangle are 3, $4$, and $x$. Then the range of $x$ is ( ).
(A) $1<x<7$
(B) $5<x<$ ?
(C) $1<x<\sqrt{7}$
(I)) $5<x<7$ or $1<x<\sqrt{7}$
2. (i)).

If $x$ is the longest side, then by the cosine rule we get $5<x<7$; if $x$ is the shortest side, then by the cosine rule we get $1<x<\sqrt{7}$.