The salinity of seawater has remained about the same for millions of years—perhaps even a billion years.

Why?

(a) Salts stopped forming in the ocean long ago.

(b) Salts are included in the molecular formula of seawater.

(c) Salts are removed from seawater about as fast as they are deposited.

(d) Actually, there is more salt in the ocean today because salts are continuously washed into the sea.