DTV 40
In 1995 Richard Stallman, a well-known critic of the patent system, testified in Patent Office hearings that, to test the system, a collegaue of his had managed to win a patent for one of Kirchhoff's laws, an observation about electric current first made in 1845 and now included in virtually every textbook of elementary physics.
A. laws, and observation about electric current first made in 1845 and
B. laws, which was an observation about electric current first made in 1845 and it is
C. laws, namely, it was an observation about electric current first made in 1845 and
D. laws, an observation about elecric current first made in 1845, it is
E. laws that was an observation about electric current, first made in 1845, and is
答案 A (考平衡, 同位語, 指代....屬破裂句型, 可否請大大解說)