The test writers are looking for the Account's relationship to the Warehouse, not the Warehouse's relationship to the Account. That means you have to plug in each word to determine which correctly describes the relationship. Examine the following four sentences.
The Account has a Parent-Child relationship to the Warehouse.
The Account has a Master-Detail relationship to the Warehouse.
The Account has a Lookup relationship to the Warehouse.
The Account has a One-to-Many relationship to the Warehouse.
Clearly, since many Warehouse records can belong to a parent Account, both Lookup and Master-Detail are immediately eliminated.
The remaining two choices, Parent-Child and One-to-Many are actually opposites. This is because hyphenated relationships like Parent-Child and Master-Detail refer to the "other" object first, then to the object in question. For example, we often say the following:
The Warehouse has a Parent-Child relationship to the Account.
The Warehouse has a Lookup relationship to the Account.
The Warehouse has a Master-Detail relationship to the Account.
The only choice left is where we have One-to-Many:
The (One) Account has (Many) Warehouse records.
This question is intentionally deceptive by mentioning things like Ownership, which from the Account's perspective, doesn't matter. Unfortunately, this type of question is one of those that you'll want to think about carefully and re-read a few times. Certification questions sometimes require a bit of lateral thinking, such as what you'd have to do if you were an actual developer.