目前规模化猪场常用的补铁方式是（       ）。
(The iron supplementation method commonly used in large-scale pig farms is (         ).) A.
拌喂 
(mix) B.
滴鼻 
(nasal drops) C.
肌肉注射
(intramuscular injection) D.
静脉输液
(intravenous fluids)