20. In glycoproteins, the carbohydrate moiety is always attached through the amino acid residues:
(A)asparagine, serine, or threonine.
(B) aspartate or glutamate.
(C) glutamine or arginine.
(D) glycine, alanine, or aspartate.
(E) tryptophan, aspartate, or cysteine.
答案：99
統計：A:0,B:0,C:0,D:0,E:0
難度：計算中