Why have ukrainians sometimes called their country “little russia”?

Second largest country on the European continent, behind only Russia, Ukraine, whose name in the Slavic language means "Border", is limited to the south with Moldova, southwest with Romania, Hungary and Slovakia, west with Poland, to the northwest with Belarus, to the northeast with Russia, and to the south to the south by the Black Sea.

Ukraine was one of the main countries of the extinct Union of Soviet Socialist Republics (USSR). That's why it is and is still known today as "Little Russia". In 1920, its territory was controlled by the communists who, taking advantage of the fertility of the Ukrainian soil (“black earth”), developed large cereal plantations. National independence was proclaimed on July 16, 1990, and was approved on August 24 of the same year. Since then, the nation has joined the Commonwealth of Independent States (CIS) - a group formed by Russia and the former Soviet republics.

the answer is b. apsidal precession