The output from line 5 of the Test class would be 10.

Explanation:

In the Test class, there is an instance variable x with a value of 12.

The method takes a parameter x and performs an addition operation x += x, which is equivalent to x = x + x.

When the method is called with an argument of 5 (t.method(5)), the local variable x inside the method is set to 5.

The addition operation x += x is then performed, resulting in x being updated to 10.

Finally, System.out.println(x) prints the value of x, which is 10.

Therefore, the output from line 5 of the Test class would be 10, so the correct answer is C.