下列函数中，在x=0处不可导的是(  )．

A 当f’(x)<0时，f(<img width="24" height="62" src="https://www.beizhujiaoyu.com/uploads/202208/20210520000956_1953.gif" />)<0 B 当f’’(x)<0时，f(<img width="24" height="62" src="https://www.beizhujiaoyu.com/uploads/202208/20210520000956_1953.gif" />)<0 C 当f'(x)>0时，f(<img width="24" height="62" src="https://www.beizhujiaoyu.com/uploads/202208/20210520000956_1953.gif" />)<0 D 当f”(x)>0时，f(<img width="24" height="62" src="https://www.beizhujiaoyu.com/uploads/202208/20210520000956_1953.gif" />)<0

A M>N>K B M>K>N C K>M>N D K>N>M

A C '(Q₀)=0 B C’(Q₀)=C(Q₀) C C’(Q₀)=Q₀c(Q₀) D Q₀C'(Q₀)=C(Q₀)

A <img width="115" height="106" src="https://www.beizhujiaoyu.com/uploads/202208/20210520001020_1639.jpg" /> B <img width="115" height="106" src="https://www.beizhujiaoyu.com/uploads/202208/20210520001020_3826.jpg" /> C <img width="116" height="106" src="https://www.beizhujiaoyu.com/uploads/202208/20210520001022_6795.jpg" /> D <img width="115" height="106" src="https://www.beizhujiaoyu.com/uploads/202208/20210520001022_8514.jpg" />

A r(A，AB)=r(A) B r(A，BA)=r(A) C r(A，B)=max{r(A)，r(B)} D r(A，B)=r(A^T，B^T)

A 0．2 B 0．3 C 0．4 D 0．6

A <img width="167" height="47" src="https://www.beizhujiaoyu.com/uploads/202208/20210520001026_8993.jpg" /> B <img width="204" height="47" src="https://www.beizhujiaoyu.com/uploads/202208/20210520001027_0857.jpg" /> C <img width="167" height="48" src="https://www.beizhujiaoyu.com/uploads/202208/20210520001029_0075.jpg" /> D <img width="204" height="48" src="https://www.beizhujiaoyu.com/uploads/202208/20210520001029_2576.jpg" />