Based on the latin root "flux" as it is used in "influx" which statement best tells the meaning of the underlined word in the paragraph?

mrs. smith suffered from acid reflux disease. she had an operation to keep her stomach acid from moving the wrong way. then she felt better and could eat normally again.

a.
the acid moved too slowly.

b.
the acid flowed backward.

c.
the acid circled around.

d.
the acid passed by the stomach.