问题
ood news! Such a successful gene ______ in pigs that it enables the pigs to produce human serum albumin, a protein made by the liver. Look! Here ________.
A:have they modified…they come.
B:did they modify…come they
C:they have modified…are coming they
D:they modify…they are coming;
B:did they modify…come they
C:they have modified…are coming they
D:they modify…they are coming;
正确答案是：
