Which of the following did not result in an output error in PHP 4 but does in PHP 5?

Which of the following did not result in an output error in PHP 4 but does in PHP 5?

A.
Using ‘var’ as an access modifier.

B.
Assigning a new object instance to $this in a constructor.

C.
Passing an object by-reference.

D.
Passing an object by-value.