To answer this question, let's go through each option to understand why it is correct or incorrect:
Option A) Compilation error: Divisions must be in a try block - This option is incorrect. Divisions do not need to be in a try block. A try block is only necessary when there is a possibility of an exception being thrown.
Option B) Compilation error: DivideByZeroException - This option is incorrect. Although dividing by zero is an error, the code will compile without any issues.
Option C) Runtime Exception - This option is incorrect. The code will not throw a runtime exception.
Option D) No Error: a is NaN - This option is correct. When dividing any number by zero in Java, the result is not a number (NaN).
The correct answer is D. No Error: a is NaN. This option is correct because dividing by zero in Java results in NaN (Not a Number) without any compilation or runtime errors.