钢材双面角焊缝的标注方法，正确的是下列哪一种?

• A.<img src="https://timg.fentiku.com/101/2016/10/21/zBsf5UiNYS.png" title='zBsf5UiNYS.png' alt='zBsf5UiNYS.png'/>
• B.<img src="https://timg.fentiku.com/101/2016/10/21/I3145rfmUQ.png" title='I3145rfmUQ.png' alt='I3145rfmUQ.png'/>
• C.<img src="https://timg.fentiku.com/101/2016/10/21/vRsGFG6Ke1.png" title='vRsGFG6Ke1.png' alt='vRsGFG6Ke1.png'/>
• D.<img src="https://timg.fentiku.com/101/2016/10/21/Fk7CqRAND1.png" title='Fk7CqRAND1.png' alt='Fk7CqRAND1.png'/>

正确答案：C