Final answer:
Without the actual histogram, we cannot confirm the shape of the distribution of structures built in Denver County. However, the shape is described based on whether there is a central peak and how the data tapers off, indicating whether it's bell-shaped or showing variance.
Step-by-step explanation:
The question refers to the analysis of the shape of the distribution of structures built in Denver County as shown on a histogram. When describing the shape of a histogram, we often refer to whether it is bell-shaped (symmetrical with tails at each end), uniform, skewed, or has a particular pattern such as a hump or a V-shape. Unfortunately, without a visual representation of the histogram, we cannot definitively say if the shape is bell-shaped, has little variance, or a lot of variance.
However, we can discuss the options: A bell-shaped histogram means most of the data points are around a central peak and the frequencies decrease symmetrically at both ends. So if the histogram with the number of structures built has a central peak during the 1950-1959 or 1970-1979 decades and tapers off on both sides, one of those statements (A or B) could be true. Otherwise, without a central peak, the distribution is not bell-shaped. When discussing variance, little variance (C) suggests that the number of structures built each decade does not fluctuate drastically, while a lot of variance (D) indicates substantial fluctuations in numbers from decade to decade.
To answer a question on a histogram's shape, one would generally draw a smooth curve through the tops of the bars (the highest point of each bar) and describe the resulting shape, whether it's uniform, bell-shaped, skewed, etc.