（）.

A f(x)=|x| sin |x| B f(x)=|x| sin<img src="https://www.beizhujiaoyu.com/uploads/202208/162138272976091.png" width="40" height="30" title="" align="" alt="" /> C f(x)=cos|x| D f(x)=cos<img src="https://www.beizhujiaoyu.com/uploads/202208/162138274372441.png" width="40" height="30" title="" align="" alt="" />

A a=3，b=1 B a=3，b=2 C a=-3，b=1 D a=-3，b=2

A 当f’(x)<0时，f(<img src="https://www.beizhujiaoyu.com/uploads/202208/162138275965501.png" width="20" height="52" />)<0 B 当f’’(x)<0时，f(<img src="https://www.beizhujiaoyu.com/uploads/202208/162138276658251.png" width="20" height="52" />)<0 C 当f'(x)>0时，f(<img src="https://www.beizhujiaoyu.com/uploads/202208/162138277130801.png" width="20" height="52" />)<0 D 当f”(x)>0时，f(<img src="https://www.beizhujiaoyu.com/uploads/202208/162138277776291.png" width="20" height="52" />)<0

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

A <img src="https://www.beizhujiaoyu.com/uploads/202208/162138279424951.png" width="19" height="52" /> B <img src="https://www.beizhujiaoyu.com/uploads/202208/162138280026421.png" width="20" height="52" /> C <img src="https://www.beizhujiaoyu.com/uploads/202208/162138280561401.png" width="20" height="52" /> D <img src="https://www.beizhujiaoyu.com/uploads/202208/162138281333591.png" width="20" height="52" />

A <img src="https://www.beizhujiaoyu.com/uploads/202208/162138282628691.png" width="96" height="85" />  B <img src="https://www.beizhujiaoyu.com/uploads/202208/162138285589071.png" width="96" height="80" />  C <img src="https://www.beizhujiaoyu.com/uploads/202208/162138286356711.png" width="96" height="80" />  D <img src="https://www.beizhujiaoyu.com/uploads/202208/162138286918831.png" width="96" height="80" /> 

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^TB^T)