We _____ on this project for four hours. Let's have a rest. [ ]

A. are working

B. have been working

C. worked

D. had worked

在人际交流活动中，人际交流技巧都与人的“传播器官”有关。它们有言语器官、视觉器官和（）

A.中枢器官

B.神经系统

C.感觉器官

D.听觉器官

E.感知系统