What is the missing reason in the proof?

Prove –(–y – x) – x = y

–(–y – x) – x = –[–y +(–x)] – x
Definition of subtraction

–[–y +(–x)] – x = y + x – x
Opposite of a sum property

y + x – x = y + x + (–x)
Definition of subtraction

y + x + (–x) = y + [x + (–x)]
Associative property of addition

y + [x + (–x)] = y + 0
Additive inverse property

y + 0 = y
(blank)

Answer options for (blank):

A. Symmetric Property

B. Additive Inverse Property

C. Additive Identity Property

D. Opposite of a Sum Property