A:—CO—NH—
B:游离的氨基
C:游离的羧基
D:R基
One day Eddie and Hobo looked at the ____. Eddie thought he saw a____but Hobo thought it was a ____. Because Hobo saw one ____. Eddie thought there were many bright ____and it was too____, so it couldn't be a plane.
在比例尺为1:100000的地图上,两地图上距离为3厘米,则实地距离是( )