图示刚架中，哪一个刚架的横梁跨中弯矩最大？

• A.<img src="https://timg.fentiku.com/97/2016/12/22/COa2tvJ4kc.png" title='COa2tvJ4kc.png' alt='COa2tvJ4kc.png'/>
• B.<img src="https://timg.fentiku.com/97/2016/12/22/Cap9JIMt92.png" title='Cap9JIMt92.png' alt='Cap9JIMt92.png'/>
• C.<img src="https://timg.fentiku.com/97/2016/12/22/wLaIp3UA1L.png" title='wLaIp3UA1L.png' alt='wLaIp3UA1L.png'/>
• D.<img src="https://timg.fentiku.com/97/2016/12/22/uMG2pNJEH2.png" title='uMG2pNJEH2.png' alt='uMG2pNJEH2.png'/>

正确答案：B