Answer:
C. 
Step-by-step explanation:
You can solve this in two ways, firstly by eliminating all the wrong answers, and secondly by just knowing that the horizontal line in 
means that we are talking about a line.
This is how we solve this question by using the eliminating process.
(A. ∠C) is not the right answer because the ∠ sign lets us know that this answer represents an angle, not a line
(B. <em>B) </em>is not the right answer because it represent a point, not a line (in math we use a singular capital letter to represent points)
(D. ΔABC) is not the right answer because the Δ sign lets us know that the answer represents a triangle, not a line.
Therefore, the only option left is C. 
It was stated in the problem that a given volume of a is inversely proportional with the pressure of the system. It means that the as the volume increases, the pressure would decrease and as the volume decreases, the pressure would increase. We would express it as:
V α 1/P
To change it to an equality, we introduce a proportionality constant, k. We do as follows:
V = k/P
So, to determine what is asked, we need to first calculate for the value of k.
V = k/P
At V = 160 m^3 P = 108 cmHg
160 = k / (108)
k = 17280
Thus, at P = 87 cmHg
V = 17280 / 87
V = 198.62 m^3
Find the side length:
Side = 68/4 = 17
Now use Pythagorean theorem:
Diagonal = sqrt(17^2 + 17^2)
Diagonal = sqrt(289 + 289)
Diagonal = sqrt(578)
Diagonal = 24 feet
The answer is B. 24 feet
The answer is d not enough information