Which of the following is a valid doctest?
Which of the following is a valid doctest?
a.
def add(x, y): """Returns sum of two numbers. """ >>> add(5, 6) 13 return x + y
b.
def add(x, y): return x + y
c.
def add(x, y): """Returns sum of two numbers. >>> add(5, 6) 13 """ return x + y
d.
def add(x, y): """Returns sum of two numbers. add(5, 6) 13 """ return x + y