A rapid courier system established by Chengiz Khan was known as:

Correct option is B

The rapid courier system established by Chengiz Khan was known as Yam.

Yam was the sophisticated and highly efficient postal and logistics network used by the Mongol Empire. It utilized a series of well-supplied relay stations (called urts or yams) spaced about 20 to 40 miles apart across the vast empire.Couriers, riding excellent horses and carrying an official plate (paiza or gerege), could travel at high speeds, ensuring rapid communication and intelligence gathering, which was vital for governing the massive empire.

Additional Knowledge

Gerege - The Mongol passport or safe-conduct tablet (often made of gold, silver, or wood) carried by Mongol officials and couriers to signify their authority and allow them access to horses and provisions at the Yam stations.
Qubcur - This term is less common in this context, but it can refer to a Mongol tax or levy.
Anda - A Mongol term for a solemn, sworn blood-brotherhood or covenant.