[Nemesisof99]

The question -->
R-X + Mg -----(dry ether)-----> R-MgX
X could be -
a) Flourine
b) Chlorine
c) Bromine
d) Iodine

I marked Chlorine, Bromine and Iodine but the book says Chlorides can't form Grignard product in dry ether solvent but in THF medium..I've read contradictory facts in another book..Help pls.