What is the most expensive element?

Who is better, messi or cristiano, i need this for a chemistry class. asap

The movement of tectonic plates and in two locations is described below: location a: tectonic played push together location b: tectonic plates push apart

Pl what kind of reaction is this? nahco3 + h2o → co2 + naoh + h2o -composition -decomposition -single replacement -double replacement im leaning more toward single replacement. if im wrong can you explain whyy?