Instrument that I used to open locks

By definition, we have to:

A key is an element commonly used to open locks where there are some objects that are intended to protect

Theodore of Samos in the seventh century BC invented the keys.

The largest number of keys used are metal (steel or aluminum), its use is to open the lock by entering it and turning.

Answer:

Instrument that I used to open locks is:

The keys.

Depends on what your choices are, could be a key but my first thought was a lockpick.