To choose the most appropriate word to complete the sentence, we need to consider the context in which someone might "feel" something. Let's break down the meanings of the words:

Annoyed: Feeling slightly irritated or disturbed, often by something small or minor.
Frustrated: Feeling upset or disappointed because something isn't going as planned or because of difficulty achieving a goal.
Depressed: Feeling very sad, hopeless, or overwhelmed, often without a specific cause, and can sometimes lead to a lack of motivation or energy.
Since the sentence only says "Lan is now feeling ______," without additional context, "frustrated" seems like a reasonable choice, as it's a common feeling people experience in various situations where things don't go as expected.

Correct answer: B. frustrated