Which sentences show standard relative-clause agreement for the supplied meaning? Select all that apply.
Of all the keys, the only one that opens this lock is brass.✓Bonne réponse
The two keys that open this lock are brass.✓Bonne réponse
Of all the keys, the only one that open this lock is brass.
The two keys that opens this lock are brass.
Explication
Opens agrees with the singular key identified as unique, while open agrees with the plural antecedent two keys. The competing sentences assign the opposite number to the relative verb despite the explicit meaning or plural subject.