17. Which of the following bond-pairs within a peptide backbone show free rotation around both bonds?
(A) N-Ca and N-C
(B) Ca-C and N-Ca 
(C) C=O and N-C
(D) C=O and N-Ca
(E) N-C and Ca-C.

答案：登入後查看
統計： A(0), B(4), C(0), D(0), E(0) #2844110