用强酸滴定强碱时,若选用甲基橙作指示剂,当达到滴定终点时溶液的颜色变化是( )
A:由红变橙
B:由黄变橙
C:由黄变红
D:由红变黄
—Where's Sam?
—He _______ for a test in his room.
下列措施中,不属于预防接种的是()