The principle given only talks about an agreement with a "boy" below eighteen years of age being unenforceable. The facts describe an agreement with a "girl" who is seventeen. Since the principle strictly refers to a boy and the facts describe a girl, we need to check whether the principle can be applied here at all.
Since the principle is worded specifically for a "boy" and the facts describe a "girl," the principle cannot be applied to reach either an enforceable or unenforceable conclusion.
Therefore, the correct answer is No inference can be drawn.
The principle can be read as a conditional rule: if a person is a boy below eighteen years of age, then an agreement with that person is not enforceable by law. The rule is written narrowly around one specific category of person, a boy under eighteen. Here the facts describe an agreement with a girl of seventeen, so before reaching any conclusion we need to check whether the facts actually satisfy the condition the rule is built around.
Because the given rule's condition is limited to a boy under eighteen and the facts involve a girl instead, the condition needed to trigger the rule is never met, leaving no basis for any conclusion either way.
Therefore, the correct answer is No inference can be drawn.