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right, Chloromethane + Mg (dry ether) gives grignard reagent CH3MgCl.
CH3MgCl + CO2 --> CH3C.O.OMgCl
CH3C.O.OMgCl + HCl --> CH3COOH (ethanoic acid)

what's question 1c?
Thank you to you both. it was a great help.