-They are quiet, aren't they?  

-Yes. They are accustomed ___________at meals.  [ ]

A. to talk          

B. to not talk  

C. to talking      

D. to not talking

一座无吊车的厂房，屋架间距为6m，屋架柔性系杆的断面应选择下列中的哪一种（）？

A.∠56×5，i_x=1.72cm，i_min=1.10cm

B.∠63×5，i_x=1.94cm，i_min=1.25cm

C.∠70×5，i_x=2.16cm，i_min=1.39cm

D.∠75×5，i_x=2.32cm，i_min=1.50cm