【单选题】By '...challenges explanation' (Line 2, Para. 1) the author means that______.
A.
no explanation is necessary for such an obvious phenomenon
B.
no explanation has been made up to now
C.
it's no easy job to provide an adequate explanation
D.
it's high time that an explanation was provided
【单选题】直肠肛管周围脓肿中哪种是临床上最常见的()
【单选题】变阶处Ⅱ1-Ⅱ1截面弯矩与( )项值接近。
【单选题】临床上最常见的直肠肛管周围脓肿类型,是( )
【单选题】变阶处Ⅱ1-Ⅱ1截面弯矩与下列______项值接近?
【简答题】作图示结构的M图。已知P=6kN,q 1 =1kN/m,q 2 =4kN/m,M 1 =12kN·m,M 2 =40kN·m。