Identify A and B in the `CH_3Br + Mg ("ether") to A overset(H_2O)toB`.

Explanation

To solve the question, we need to identify the compounds A and B in the reaction sequence given:

1. **Starting Material**: CH₃Br (Bromomethane)
2. **Reagent**: Mg in ether
3. **Product A**: Formed from the reaction of CH₃Br and Mg
4. **Reagent**: H₂O
5. **Product B**: Formed from the reaction of Product A with H₂O

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