We really have to be careful because the situation is rather tricky.

Analyze the question: The underlined word is tricky (the underline doesn't show here, but "tricky" is the word the question is testing). We need the option closest in meaning to "tricky" as used in the sentence.

Explain the concept: "Tricky" has more than one meaning:

• Deceitful or sly (describing a person who tricks others)
• Difficult or delicate, needing careful handling (describing a situation or task)

Context decides which meaning applies.

Step-by-step solution:

1. The sentence says: "We really have to be careful because the situation is rather tricky."
2. "Tricky" describes a situation, not a person. A situation is not usually "deceitful," so A is unlikely.
3. The need to "be careful" shows the situation is delicate and hard to handle, not unimportant. So B (trivial) is wrong, since a trivial matter would need no special care.
4. "Unexpected" (C) describes something that was not anticipated. It does not explain why we must be careful.
5. "Difficult" (D) fits perfectly: a situation that is awkward and hard to handle requires care.

Answer: D. difficult.

Tip: In "closest in meaning" questions, always test each option by substituting it into the sentence. Here, "the situation is rather difficult" makes perfect sense. Also check what the word describes: if it describes a situation or task, "tricky" usually means difficult. If it describes a person, it usually means cunning.