What is a key feature of the RPG-7 Tandem HEAT round?

The key feature of the RPG-7 Tandem HEAT round is its multi-stage warheads with a secondary charge. This design is crucial for defeating modern reactive armor found on many armored vehicles. The first stage of the tandem warhead is designed to initiate the armor's reactive protection system, effectively neutralizing it by setting off the reactive armor's explosive material. Once this protection is compromised, the second stage follows closely behind, penetrating the base armor of the target vehicle.

This two-step mechanism allows the RPG-7 to maintain its effectiveness against advancements in armored vehicle protection, making it a versatile and lethal weapon in modern warfare. The other options do not align with the specific characteristics and capabilities of the RPG-7 Tandem HEAT round; hence they do not provide the same level of effectiveness against armored targets.