Final answer:
Encoding and storing a friend's new cellphone number typically involves c) effortful processing. This refers to the encoding of information that requires conscious effort and attention. Active engagement in effortful processing helps enhance memory and ensure information retention.
Step-by-step explanation:
Encoding and storing a friend's new cellphone number typically involves effortful processing. Effortful processing refers to the encoding of information that requires conscious effort and attention. When you actively work to store the new cellphone number in your memory, such as repeating it, linking it to existing knowledge, or thinking about its meaning, you are engaging in effortful processing. This helps to enhance memory and ensure that the information is retained for later retrieval.