Third person plural pronoun is THEY.
If you want to create a possessive pronoun out of that one, that would be THEIRS.
Possessive pronouns, as the name itself says, determine some kind of possession. For example:
Is this books yours? - No, it's theirs.
The answer here is B, because in the second paragraph, it says that the team never got the parts
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This is A. declarative because it is simply stating a fact rather than telling someone to do something (imperative), making a dramatic exclamation, or asking a question