A Helix-Turn-Helix Motif Can Best Be Described as A(n) Followed $\alpha$

A helix-turn-helix motif can best be described as a(n) followed by a(n) .

A) " $\alpha$ -helix; $\beta$ -helix"
B) " $\alpha$ -helix; $\alpha$ -helix"
C) " $\beta$ -helix; $\beta$ -helix"
D) " $\beta$ -helix; $\alpha$ -helix"