Have Mercy on us, O Lord.
For we have sinned against you.
Show us, O Lord, your mercy.
And Grant us your salvation.
Our late pastor used this option almost exclusively except in Advent and Lent (where he used the Confitieor). Our current pastor has been using it as part of the “rotation.” He uses the Confitieor during Advent and Lent, and alternates this and Option C during Ordinary Time.
Other than these two priests, I never saw Option B used. It is sad that it is so under-utilized because it is beautifully penitential when chanted. It sounds plaintive, contrite and sincere when chanted correctly.