What is the smallest unit you can add to a LocalTime object?
plusNanos are the smallest units available, making Option C correct.
Option D is incorrect because LocalTime is not that granular.
Note that while you can add milliseconds by adding many nanoseconds, there isn't a method for it.
A millisecond is also larger than a nanosecond.
LocalTime is immutable. You can add time and it gets returned as a different object.