单项选择题
Intravenous injection of dl-tetrahydropalmatine,corydalis L ord-corydaline affordedanalgesic actions in rabbits．The first two agents had stronger actions than the latter．镇痛作用最弱的物质是（）
A．dl-tetrahydropalmatine
B．corydalis L
C．d-corydaline
D．corydaline and corydalis L
E．d-corydaline and dl-tetrahydropalmatine