If a Transmembrane Domain of Protein Contains $\beta$ -Sheet Structure, the Overall Structure of the Transmembrane Portion Is

If a transmembrane domain of protein contains $\beta$ -sheet structure, the overall structure of the transmembrane portion is likely a ____________.

A) $\beta$ -barrel
B) $\beta$ -tube
C) $\beta$ -turn
D) $\beta$ -helix
E) none of the above