Which of the Following Applications Would a Crown Ether Typically

Which of the following applications would a crown ether typically not be used for?

A) as a chelating agent to remove heavy metals from water
B) to capture minute amounts of precious metals from seawater
C) as a means to indirectly bring reactive anions into nonpolar solvent media
D) to study the chemistry of "host-guest" complexation
E) to stabilize Grignard and organolithium reagents