سوال ۲۰ کنکور ارشد ریاضی ۱۴۰۱

Read the passage and complete the sentence.

PASSAGE (excerpt): "The theory of interpolation has been enriched recently by what is known as spline interpretation methods. Usually a spline is a piecewise-polynomial function defined in the region D, i.e., a function for which there exists a decomposition of D into subregions in each of which the function is a polynomial of some degree m. Also the function, as a rule, is continuous in D, together with its derivatives to order m - 1, and the mth derivatives are square integrable. In practice, the most often used polynomials are cubics."

Piecewise polynomial ----------.