如題，網(wǎng)站沒(méi)有修改過(guò)任何東西，突然出現(xiàn)

Fatal error:  Call to undefined function Think\C() in /www/wwwroot/www_XXXXXXXl/Include/Library/Think/Think.class.php on line 313

請(qǐng)教各位大大，應(yīng)該怎么處理才可以正常恢復(fù)啊？