In general compile time errors means your application/.java file won't compile, so you won't be able to run it and therefore won't get any runtime errors. A compile time error usually consists of syntax errors, or importing (or lack there of) of packages and such.
ex: String s = "wow"; s.delete(1,2); //won't compile because delete doesn't exist in String
Runtime errors are errors that can not be caught in compile time, like indexOutOfBounds, division by zero, etc. These errors typically occur because of certain end cases that are not handled.
ex: System.out.println(args); //this could throw an IndexOutOfBoundException
First thing you can always do for the exam is that check for choices in the given answers/options, if there is a choice for 'compile-time error' then you need to hunt for its possibility in the code, else you can start following through the logic. I dont think there are any runtime errors, only runtime exceptions on exam.