Misc: H2S04 is the chemical formula for which compound?

Questions

A _______ is a pact between a secular authority & the church.?

A _______ is the only standard international unit of measure still defined by a physical object, a bar composed of two elements?

A ________ can eat only when its head is upside down?

A __________ can learn to recognize itself in a mirror?

A __________________ measures blood pressure?