蛋白质抗原首次免疫接种后,最好间隔多长时间进进行第二次免疫()
A.7~10d
B.10~20d
C.20~30d
D.30~60d
E.3个月
参考答案:B
根据目前海关的规定,申请成立专业报关企业应由各直属海关批准后,报海关总署备案。 ( )
Who first gave baseball a standard set of rules
A.Abner Doubleday.
B.Alexander Cartwright.
C.Albert Spalding.
D.Babe Ruth.