平板网架跨度L在30m之内，其高度为( )。

• A.<img src="https://timg.fentiku.com/97/2016/12/22/40O6JYgvxi.png" title='40O6JYgvxi.png' alt='40O6JYgvxi.png'/>
• B.<img src="https://timg.fentiku.com/97/2016/12/22/OIL1VrdaMp.png" title='OIL1VrdaMp.png' alt='OIL1VrdaMp.png'/>
• C.<img src="https://timg.fentiku.com/97/2016/12/22/k73uFQmMPz.png" title='k73uFQmMPz.png' alt='k73uFQmMPz.png'/>
• D.<img src="https://timg.fentiku.com/97/2016/12/22/84T9qg4NHb.png" title='84T9qg4NHb.png' alt='84T9qg4NHb.png'/>

正确答案：B