World Rivers – Commonwealth of Independent States (CIS) Which river is the longest within the CIS region, considering total river-system length?

Introduction / Context:
The Commonwealth of Independent States (CIS) includes several countries of the former USSR, dominated geographically by Russia’s vast river systems. Knowing the relative lengths of major rivers is a classic general-knowledge topic—especially distinguishing the great Siberian rivers from the long but European-limited Volga.

Given Data / Assumptions:

• Candidates include Ob, Irtysh (a major tributary of Ob), Yenisei, and Volga.
• We consider standard total system lengths used in atlases.
• Only one is the longest across the CIS as a whole.

Concept / Approach:
The three giant Siberian rivers—Ob (with Irtysh), Yenisei, and Lena—are among the world’s longest. Of the options given, the Yenisei–Angara–Selenge system generally edges the Ob–Irtysh system and far surpasses the Volga in length. The Volga is Europe’s longest but is shorter than the leading Siberian systems.

Step-by-Step Solution:
Identify that Irtysh is a tributary of the Ob; it is not longer as a standalone system.Compare system lengths: Yenisei system > Ob–Irtysh system > Volga.Select “Yenisei river.”

Verification / Alternative check:
Standard references list approximate lengths: Yenisei system over 5,000 km; Ob–Irtysh also over 5,000 km but generally measured slightly less than the Yenisei; Volga about 3,500+ km.

Why Other Options Are Wrong:

• Irtysh river: important tributary, not the overall longest system.
• Ob river: very long, but typically marginally shorter than the Yenisei system in total length.
• Volga river: longest in Europe, yet significantly shorter than the great Siberian rivers.

Common Pitfalls:
Assuming “longest in Europe” equals “longest in CIS.” The CIS includes Siberia, which hosts much longer rivers.

Final Answer:
Yenisei river