Which of the following is a basic evolutionary advance needed to convert a down-like feather into a primary flight feather. a. The feathers rachis must be lengthened and reshaped to help support the birds weight
b. Down like feathers must become smaller in size
c. Down like feathers must grow out more quickly
d. Preening behavior must be eliminated from bird behavior
e. Adhesive proteins must be formed more quickly

answer: b: experiments that showed that all cells are similar in how they metabolize and in their composition

explanation:

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.