Which of the following statements is correct after executing the following program?

list_a = [1,2,3] list_b = list_a list_a[-1] = 999 

Select one:

a. list_a is [1, 999, 3]

b. list_b is [1, 2, 999]

c. list_b is [1, 2, 3]

d. list_a is [1, 2, 3]