No diagram with question.
http://firelink.monster.com/nfs/firelink/static/620.pdf
C is the correct answer. The alternatives differ in two important ways. The first concerns the level of the house on which the fire is located. Alternatives C and D indicate that the fire is in the basement, thus leaving little room for confusion. In contrast, alternatives A and B use the term lower level. Lower level could be interpreted as the basement or as the lowest above-ground level in the house. Since the term lower level is more likely to confuse the reader of the report than the term basement, responses C and D are better than responses A and B.
Second, the alternatives differ in the detail used to describe the area of the basement in which the fire is located. Alternatives B and C use more detail by stating, In the southeast comer. This detail allows us to break the basement up into four sections and gives us a very specific idea of where the fire is located. In contrast, alternatives A and D use, in the rear. This allows us to break the basement up into only two sections front and rear and gives us a less specific idea of where the fire is located.
Combining the above two ideas, C is the best answer.