To answer this question, we need to understand the size of the Java primitive data type "long."
The Java primitive data type "long" is a 64-bit signed integer. It can hold values ranging from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807.
In Java, the size of a "long" data type is always 8 bytes. This is because the Java language specification defines "long" as a 64-bit data type, which means it requires 8 bytes of memory to store its value.
Therefore, the correct answer is:
D. 8