Which of the following objects has polarity? A
the Earth, which has magnetic north and south poles

B
the city of Chicago, which has a North and Southside

C
a map of the country, which has a compass pointing north

D
an unmagnetized block of metal, which has a top and a bottom

D

An unmagnetized block of metal, which has a top and a bottom

answer; /// i do believe that the correct answer is (c)nuclear bond

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.