Final answer:
The spacebar item in The Binding of Isaac that allows firing a blue flame for up to 184 damage and is unlocked by donating 900 coins to the Shop is The Candle.
Step-by-step explanation:
The correct answer to which spacebar item in The Binding of Isaac allows Isaac to fire a blue flame that inflicts 23 damage per tick, potentially causing up to a total of 184 damage, and can be unlocked by donating 900 coins to the Shop is A) The Candle.
The Candle is a reusable item that allows players to launch a blue flame at enemies, dealing significant damage. This powerful spacebar item is known for its utility in combat, offering both offensive capabilities and the opportunity to clear out enemy projectiles. To unlock The Candle, players must consistently donate to the shop's donation machine, reaching a total of 900 coins.