Which item is primarily used for injecting heroin?

The correct answer is syringes because they are specifically designed for the purpose of injecting substances, including drugs like heroin. Heroin is typically prepared in a liquid form by dissolving it in water, and a syringe is used to draw this solution up for injection. This method allows for quick absorption of the drug into the bloodstream, producing an immediate effect.

Other options serve different functions in the context of heroin use. Pipes might be used to smoke the drug, while spoons are commonly used to heat and dissolve solid heroin into a liquid form suitable for injection. Bags are typically used for packaging and storing the drug. Therefore, syringes stand out as the primary tool specifically meant for the injection of heroin, linking directly to its method of administration.