Final answer:
The least effective method of controlling bleeding among the given options is a tourniquet.
Step-by-step explanation:
The LEAST effective method of controlling bleeding among the given options is C. Tourniquet. Although a tourniquet can be useful in extreme situations where direct pressure or elevation is not enough to control bleeding, it is generally considered as a last resort. Tourniquets can cause tissue damage and may lead to complications, such as nerve injury or limb loss.