New to python, baffled by program output

[Lazareth S. Link]

Hiya to whoever might stumble across this.

I've recently taken up learning how to script/program in python.
I've made my first program, a simple fahrenheit-celsius converter,
both ways.
For some reason I fail to comprehend, the program writes a line of
"None" when rerun in a while loop.
Here is the code:

---START---
def choice_c():
	print
	celsius = input("Input celsius: ")
	print "Fahrenheit: ",cel_fah(celsius)
	print

def choice_f():
	print
	fahrenheit = input("Input fahrenheit: ")
	print "Celsius: ",fah_cel(fahrenheit)
	print

def cel_fah(placeholder):
	return 9.0/5.0*placeholder+32

def fah_cel(placeholder):
	return (placeholder-32.0)*5.0/9.0

def options():
	print "press 'c' to convert celsius to fahrenheit."
	print "press 'f' to convert fahrenheit to celsius."
	print "press 'q' to exit program."

choice = "n"
options()
while choice != "q":
	choice = raw_input("Choice: ")
	if choice == "c":
		choice_c()
	elif choice == "f":
		choice_f()
	print options()
---END---

Any of you know why it prints that line? Is is just my comp?
If any applies, how to get around it?
Would greatly appreciate the help.