Natural populations fluctuate through time. One of the forces causing variation in population size is variation in the physical environment, which can have both direct and indirect effects on populations. Variation in population size linked to environmental factors (aside from those that occur daily or seasonally) is likely to:

A) be predictable and constant.
B) be density-dependent.
C) affect the biotic potential exponentially.
D) be irregular, perhaps even random.
E) track the logistic growth model.

the areas around the equator

the answer is true when observing or determining population size, a direct observation is use, in which each organism is counted in a population or in an area. one benefit of this measure is that you get the exact population count but it will take a long time to  determine  the  size  of a  population.

answer-

the statement that f(x) = |x+a| + b has exactly one x-intercept is sometimes correct.

solution-

it solely depends on b, whether the function will have one or two or zero x intercept.

this plot of the given function, f(x) = |x+a| + b will be the basic absolute value graph i.e v shape, with vertex translated to (-a, b), instead of origin.

1-   if b is zero, the graph will have exactly one x-intercept, at x= -a

2- if b is positive, the whole graph will be above the x-axis, hence it will have no x-intercepts.

3- if b is negative, the graph will be below the x-axis, hence it will have two x-intercepts.

∴ the statement is sometimes true.