A.自愿B.匿名C.保密D.無(wú)害
A.起點(diǎn)B.出發(fā)點(diǎn)C.起點(diǎn)和出發(fā)點(diǎn)D.起點(diǎn)和終點(diǎn)
A.日常觀(guān)察B.直接觀(guān)察C.間接觀(guān)察D.一般觀(guān)察