Which is not present in Grignard reagent

Metal present in Grignard reagent is

Name the metal that is always present in a Grignard reagent.

The metal present in Grignard reagent is:

Grignard reagent is usually prepared by R-X+Mg overset(Et_(2)O)rarrRMgX " " "Grignard reagent" Ar-X+Mg overset(Et_(2)O)rarrArMgX " " "Grignard reagent" Grignard reagent acts s a strong base. Grignard reagent carry out nucleoplilic attack in absence of acidic hydrogen. Grignard reagent form complex with its ether solvent. Complex formation with molecule of ether is an important factor in the formation and stability of Grignard reagent. Which of the following Grignard reagents is not possible ?