(The Russians) have heroically resisted disasters, foreign invasions that devastated the Russian land, lifted from ruins cities and villages. —b) признаком множественного числа имени существительного.
On September 8, 1380 Prince (Dmitry’s) army crossed Don River and took up position on Kulikovo Field. — c) показателем притяжательного падежа имени существительного.
The federal government of Russia (consists) of three branches: legislative, executive and judicial. — a) показателем 3-го лица единственного числа.
Taking advantage of plight, Swedish and German feudal lords invaded Novgorod and south to capture its (riches). — a) показателем 3-го лица единственного числа.