通关

它绕着白色拴马桩回旋，这些桩子挡住了公共汽车和二十匹骡子拉的马车的通道。

pretein-free blood filtrate methods

interest-free loan

free on board (FOB)

free from particular average【保险】

free skin graft

recombination of free radicals

molal free energy

Helmholtz free energy