Which identifier was first included in the U.S.Census Bureau survey in 2010 and is one of the fastest-growing categories in the country?

A) undocumented
B) transgender
C) immigrant
D) multiracial

The identifier "multiracial" was first included in the U.S. Census Bureau survey in 2010, reflecting the growing recognition and acknowledgment of the diverse racial backgrounds within the country. This category has shown significant growth as more individuals identify with more than one racial heritage.