Uchebnik Po Angliiskomu Iazyku Forward 5 Rk.xb Link

: Often separate booklets or digital files used for assessment, which may match the "rk" designation in your query.

: Provides interactive exercises and is available at retailers like OZON . uchebnik po angliiskomu iazyku forward 5 rk.xb

This appears to be a specific digital file extension or a shorthand code used in certain educational portals or file-sharing platforms to denote ( kontrol'nye raboty ) or workbook supplements. : Often separate booklets or digital files used