difference between "back-up" and "back-off"?

[Bharath]

English Language Tests, Intermediate level

ESL/EFL Test #165 "Phrasal Verbs (A to B)", question 6

Sandy wants to learn how to drive but she must also learn how to ......... so she can get in and out of parking spots easily.

(a) back up
(b) back behind
(c) back off

English Language Tests, Intermediate level

ESL/EFL Test #165 "Phrasal Verbs (A to B)", answer 6

Sandy wants to learn how to drive but she must also learn how to back up so she can get in and out of parking spots easily.

Correct answer: (a) back up

Your answer was: incorrect
Sandy wants to learn how to drive but she must also learn how to back off so she can get in and out of parking spots easily.
_________________________

what's the difference between "back-up" and "back-off"?

Bharath

[Conchita]

To back up is to reverse a car, in American English.

Here are two definitions for 'back off':

http://dictionary.cambridge.org/define.asp?key=94048&dict=CALD
http://dictionary.cambridge.org/define.asp?key=96523&dict=CALD