Final answer:
The item in The Binding of Isaac that converts 2 soul or black hearts into 1 red heart container is 'The Converter'. This item strategically helps players manage their heart containers for survival and progression in the game.
Step-by-step explanation:
In the game The Binding of Isaac, the item that converts 2 soul or black hearts into 1 red heart container, prioritizing the use of soul hearts first, is option A) The Converter. The Converter is an activatable item that allows players to manage their heart containers by converting less permanent forms of health (soul hearts and black hearts) into permanent red heart containers, which can be more beneficial in certain game scenarios.
This conversion can be strategically used by players to ensure survival and progress through the game's multiple levels and challenges.