Ůܽŵķȫݻһɭ. ʹֹȡľ, Ƴ˱Ĺؿ, ɱӽɭֵĴʹݻٸĽ.

Ҫٻɭִ,  [ɭִ] ͼʾϰ, ȻҪջٵɭְ. , Ҫȼյľ<link="topic:line of sight"></link>֮.
