The correct answer is 3) looks.
Here's why:
The sentence needs a simple present tense verb to express a general observation. "Looks" fits this context perfectly. The complete sentence would be: "It looks like the bus is running late. Let's catch a taxi."
* "is looking" implies a continuous action, which doesn't fit here.
* "has looked" implies a completed action in the past, which also doesn't fit the context.
Answer: 3