To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) Compilation error - This option is incorrect. The given code will not result in a compilation error because it follows valid syntax. The code initializes an integer variable a1 with the value 5 and then assigns its value to a double variable a2 after performing a type cast.

Option B) Runtime error - This option is incorrect. The given code will not result in a runtime error because there is no invalid operation or division by zero involved. The code simply performs a type cast from an integer to a double.

Option C) Runtime exception - This option is incorrect. The given code will not result in a runtime exception because there is no exceptional condition or error that would cause the program to terminate abruptly.

Option D) No error - This option is correct. The given code will execute without any error. It initializes an integer variable a1 with the value 5 and then assigns its value to a double variable a2 after performing a type cast.

The correct answer is D. No error. This option is correct because the code will compile and execute without any errors or exceptions.

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• Wrong explanation

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.

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• Wrong explanation

To answer this question, let's analyze the given code:

class A {
    public static void main(String[] args) {
        A a = new B();
    }
}

class B extends A {}

In the code, a class A is defined with a main method. Inside the main method, an object a of type A is created using the constructor of class B. Class B is a subclass of A.

Since class B extends class A, it is considered to be a subtype of A. Therefore, it is valid to assign an instance of B to a variable of type A. This is known as polymorphism in Java.

Hence, there are no errors in the given code, and the correct answer is C) No errors.

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• Wrong explanation