龈沟液()
A.是渗出液,来自牙龈结缔组织间液
B.是漏出液,来自牙龈血管
C.是漏出液,来自牙龈结缔组织间液
D.是渗出液,来自牙龈血管
E.以上都不对
参考答案:D
Franklin ____ learning privater's trade at an early age. [ ]
A. set off
B. set out
C. set about
D. set up