Choose the topic that best limits the broad subject architecture.
a. famous architects
b. historic building in europe
c. modern architectural marvels
d. the history of the golden gate bridge

D. the history of the Golden Gate Bridge

Explanation:

I think this is the correct answer because it specifically adresses one architectural construction. Remember that in all disciplines the accumulated knowledge developed over the years is too extensive to embrace. This is the reason disciplines are divided in subjects. In this case if you want to do a research you need to be able to delimit the subject, otherwise you would have so much information abailable your objectives and results would turn vague. Options A, B and C, are too broad, the information required is huge, it covers too many years of history (A and B), or too many elements to take into consideration (C). Option D, limits the information to one specific element that can be easily traced in time and space.  

can you take a picture of the passage so i can answer your question

the direction of the magnetic field produced by an electric current will change when the direction of the electric current changes. for example : if a current is flowing in a straight length of wire, the magnetic field is described by a concentric circle (using right-hand rule).