Your friend is talking about a co-worker of his. You can tell that he likes her, but he's pretending that he's not interested in her romantically. You tease him by saying:
You're obviously attracted to her.
To "be attracted to" someone means to like them. It usually means to like someone in a romantic or sexual way.
You use the phrase "attracted to someone" when you want to talk about the feeling objectively. This means that you are discussing the feeling and talking about it. When you're actually feeling attracted to someone, you don't usually directly say "I'm attracted to you."
A fact is "obvious" when it's easy for anyone to recognize it. For example, when someone asks a really easy-to-answer question, you can say:
The word "obviously" is used to modify adjectives or verbs. For example:
He obviously doesn't understand.
It's obviously a popular place to go on Friday nights.
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