The inability to recall what letters accompany the number 5 on your telephone is most likely due
a. source amnesia.
b. encoding failure.
c. retroactive interference.
d. the spacing effect.

b. encoding failure.

Explanation:

Encoding Failure is when our brain temporarily becomes unable to link our memory,failure to link number 5 with letters that accompanies it. Encoding is a term used to refer to how our brain stores and remembers the information that we have stored in a short or long term memory.

There can be failure in our encoding due to trauma or drug use.

true

could you go a bit more in depth with you question? it's quite hard to understand. as soon as you do that i will be glad to : )