Final answer:
The reason for Craig lending Bobby a shirt is not specified and could be for various reasons.
Step-by-step explanation:
In this context, the question doesn't specify the purpose for which Craig lends Bobby a shirt.
Therefore, we can assume that the reason for lending the shirt could be based on various factors.
It could be for a special event, to protect Bobby's clothing from getting dirty, or perhaps because Bobby simply forgot to bring a shirt of his own. Without more information, we can't determine the exact reason why Craig is lending the shirt.