Which word correctly completes the sentence about remembering names?

The correct choice to complete the sentence about remembering names is "that." In this context, "that" serves as a restrictive relative pronoun, specifying the particular names that are being referred to. A restrictive clause provides essential information that limits or defines the noun it modifies—in this case, the names.

Using "that" indicates that the statement pertains specifically to these names, which clarifies the meaning. For example, if the full sentence were to read, "I have a hard time remembering names that are hard to pronounce," the phrase "that are hard to pronounce" tells us which names the speaker struggles to remember.

In contrast, using "which" would imply a non-restrictive clause, suggesting additional information rather than essential clarification. "Who" typically refers to people, making it less applicable when discussing names in general. "Those" would not fit grammatically, as it points to specific items, usually plural, rather than serving the purpose of creating a clause that restricts the subject.