There's no sentence listed... but greenhorn generally means someone inexperienced or new at something. It is also a rude term used to classify recent immigrants.
Explanation:
Example: Anna moved here from Russia and still wears her Russian clothes. She's such a greenhorn!
In this sentence, greenhorn is a mean adjective meaning that Anna still carries on Russian tradition and has not adopted American traditions yet.
Answer: The 2nd one, he is doing so through an action, it's not necessarily coming out and saying "He pays attention" it's indicating it through what his actions and thoughts are.