Final answer:
The 18g (option B) needle has the largest bore size among the provided options. Needle gauge numbers are inversely proportional to their diameter, so a lower gauge number means a larger bore.
Step-by-step explanation:
The gauge of a needle represents the diameter of its lumen, the hollow inside of the needle. The larger the gauge number, the smaller the diameter of the needle bore. Therefore, when comparing needle gauge sizes, it's important to remember that the numerical value is inversely proportional to the bore size.
Choosing from the options provided:
The 18g needle has the largest bore size among the options listed. This is because, in the context of needle gauges, a lower number indicates a larger diameter. Thus, the 18g needle's bore is larger than those of 21g, 22g, and 25g needles, with 25g being the smallest among them.