Shana, once again the testers have misled you. There is only one wrong answer: D. I would say that B and C are both excellent, and that A is merely acceptable. The only objection I can find to B is that the word "with" is unnecessary, but it is definitely not wrong. I have a theory why testers make so many mistakes like this. They let their personal biases over how the language should be spoken to interfere with their judgement. However, just because they like to say something in a certain way should not give them the right to force other people to speak the same way.

A agree with Jonathan. C may be the most direct/common, but B is not wrong, and many native speakers would say that.

C is correct. I guess you can quibble about exactly how wrong B is, since sloppy native speakers might say it. Adding the ‘with’ changes the meaning: I have trouble doing something. (The problem is me) I’m having trouble with my car. (The problem is the car) And even more fun: The trouble with treating prepositions as if they don’t count is that the resulting speech is awkward and ambiguous. (Here ‘trouble’ just means ‘problem’!) Does the fact that there are three similar constructions with different meanings make English confusing? Not to me, it doesn’t! They’re a feature of language in general. It’s just that people don’t notice these things in their own language because they are absorbed through exposure.

Hi Shana! They are two distinct expressions: 'the trouble with something/someone' = the problem this thing/person generates/causes/poses "The trouble with Simon is that he never arrives on time" 'to have trouble + verbING' = to experience difficulty doing something "I'm having trouble finishing my essay"