Which statement illustrates the associative property of addition?
Select one:

a. (1+√3)² + √7= 1 + (√3+√7) ²
b.(-2+72) + 4i - 2 + (7i+ 42)
c. v 18 + 5/3 (√6 +5)
d. (51.21) + 111 – 111 + (51-21)​