Janelle and marcus and group went to the library to prepare for the presentation, but the specific book they needed wasn't

they're, there
their, there
their, they're
there, their

The question provides the following sentence and asks us to fill in the gaps: "Janelle and Marcus and group went to the library to prepare for the presentation, but the specific book they needed wasn't . The first gap refers to the group of Janelle and Marcus - so it's a group that belongs to them, or their group (possesive) The second gap refers to a place where they expected the book, and the word is "there" - it's not an abbreviation so no apostrophe is needed. their, there

A: become a alien but sound like a human