When specifying criteria in the custom autofilter dialog box, use the wildcard to specify a single character.
a. ? b. *c. 'd. both a. and b.

Answer is option a. ?                                                    

Explanation:

Wild card also called wild character or wildcard character is a symbol that is used to replace or depict one or more characters. It is also used to locate specific item in data. It is sometimes used in file searches so that the full name does not need to be typed.

Examples of wildcard are

? wild card which shows a question mark (?) represents a single character. This symbol matches a single character in a certain position.

For example

explanation:

d. long term memory