QUESTION $1$

To use curly arrows to show the flow of electrons in this mechanistic step, where

would the first arrow begin?

at a lone pair on the $Mg$ atom

at the $C=C$ double bond

at the carbonyl carbon atom

at the $C-Mg$ bond

QUESTION $2$

And to where does that first curly arrow go$?$

to the magnesium atom

to the carbonyl carbon

to the carbonyl oxygen

QUESTION $3$

And where does the second curly arrow begin?

at the carbonyl oxygen atom

at the carbonyl carbon atom

there is no second arrow