Sentence Correction

40. In 195 ROchard Stellman, a well known critic of the patent system, testified in patent office hearings that, to test the system, a colleague of his had managed to win a patent for one of Kirchoff’s laws, an observation about electric current first made in 1845 and now included in virtually every textbook of elementary physics.
a. same
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 electric current first made in 1845, it is
e. Laws that was an observation about electric current, first made in 1845, and is

Answer is A
But what is wrong with B. The “which” refers directly to the laws. I don’t see the problem can someone explain this in the simplest terms to me please.
C. doesn’t the word NAMELY make this redundant?
d. IT IS doesn’t fit the sentence by hearing it out.

Can someone explain this to me in an easy way please