To solve this question, the user needs to understand the concept of type casting and data types in programming.

The given code snippet initializes an integer variable a1 with the value 5 and then assigns that value to a double variable a2 after performing a type casting to a float.

Now, let's go through each option and explain why it is right or wrong:

A. Compilation error: This option is incorrect. The code will compile without any errors because type casting from an integer to a float is allowed in most programming languages.

B. Runtime error: This option is incorrect. The code will not result in a runtime error because the type casting from an integer to a float is allowed and will not cause any issues at runtime.

C. No errors: This option is correct. The code will execute without any errors, and the value 5 will be successfully assigned to the a2 variable after the type casting.

Therefore, the correct answer is: C. No errors.