The most famous and oldest of the Towers customs is the Ceremony of... a)Changing the Guard b)Mounting the Guard c)the

The most famous and oldest of the Towers customs is the Ceremony of the Keys. — Самой известной и старинный обычай Башни является Церемония Ключей.

The Keys are the most famous and oldest customs of the Tower.

Ключи - самая известная и старейшая традиция Башни.