Observe the following Python code: def a(n): if n == 0: return 0 else: return n'an def ban, tot): if n == : return tot else: return b(n-2, tot-2) 1) Select one: a. bo is tail recursive but a0 isn't b. Both a() and bl aren't tail recursive O c. a() is tail recursive but bo isn't d. Both al) and b are tail recursive