The correct answer is A) Mechanical seals. Mechanical seals are commonly used on modern tankers to reduce cargo pump leakage to the pump room bilge. Mechanical seals create a tight, reliable seal around the pump shaft, preventing cargo from leaking out. This is a critical safety feature, as cargo leakage in the pump room can lead to the buildup of flammable vapors, posing a serious fire hazard. The other options are not the primary means of preventing cargo pump leakage. Shaft sleeves protect the pump shaft from wear, but do not directly address leakage. Clipper seals and flinger rings are other types of sealing devices, but are not as widely used for this specific application on modern tankers.