There have been many times where I felt uncertain as to how to act. Sometimes, it's because I have to make some kind of decision, and what I choose will have a larger impact. There are also times where I'm around people I don't know very well, and therefore don't know how they expect me to act. I would feel uncertain because I have no way knowing, without a doubt, what the right choice is, or how other people expect me to be.
It depends on what the italicized phrase is. If <em>on the frozen lake </em>is italicized, then this is a prepositional phrase. Because it begins with a preposition <em>on. </em>
