图示结构中C点的竖向位移为f，转角为θ，则A点的竖向位移f应为( )。

• A.f<img src="https://timg.fentiku.com/97/2016/12/22/skKvC11Cgi.png" title='skKvC11Cgi.png' alt='skKvC11Cgi.png'/>=0
• B.f<img src="https://timg.fentiku.com/97/2016/12/22/7whO0LEmzZ.png" title='7whO0LEmzZ.png' alt='7whO0LEmzZ.png'/>=f<img src="https://timg.fentiku.com/97/2016/12/22/dg4tWOCMKd.png" title='dg4tWOCMKd.png' alt='dg4tWOCMKd.png'/>
• C.<img src="https://timg.fentiku.com/97/2016/12/22/zBpeIPvCDv.png" title='zBpeIPvCDv.png' alt='zBpeIPvCDv.png'/>
• D.<img src="https://timg.fentiku.com/97/2016/12/22/F85BupmQX5.png" title='F85BupmQX5.png' alt='F85BupmQX5.png'/>

正确答案：C