I think is A. CH2CH3
so in a metal alkyl compound, β-hydrogen elimination occurs when a hydrogen atom (β-hydrogen) is abstracted from the carbon atom adjacent to the metal-carbon bond.
and then the σ-bonded R group that could undergo β-hydrogen elimination is the one that has a hydrogen atom on the carbon atom adjacent to the metal-carbon bond
A. CH2CH3 has a hydrogen atom on the β-carbon.
correct me I’m wrong