当x→0时，下列哪一个无穷小是x的三阶无穷小。（）

• A.<img src="https://timg.fentiku.com/javaimportItems/b402ff216b2d4c2bbebdb4f22b7e3ae8/images/ff17d.png"><br/>
• B.<img src="https://timg.fentiku.com/javaimportItems/b402ff216b2d4c2bbebdb4f22b7e3ae8/images/fff23.png"><br/>
• C.<img src="https://timg.fentiku.com/javaimportItems/b402ff216b2d4c2bbebdb4f22b7e3ae8/images/102114.png"><br/>
• D.<img src="https://timg.fentiku.com/javaimportItems/b402ff216b2d4c2bbebdb4f22b7e3ae8/images/103140.png"><br/>

正确答案：B