According to the rivet model of community structure, a) species share a community because of similar abiotic requirements. b) communities generally lack sharp geographic boundaries. c) if a species disappears from the community, its role will be assumed by another species. d) all species in a natural community contribute to the community's integrity. e) dependence on a particular type of soil rivets plant species into a tightly networked community.

D) all species in a natural community contribute to the community's integrity.

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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.