【名词&注释】
体外受精(in vitro fertilization)、静脉注射(intravenous injection)、皮下注射(subcutaneous injection)、知识点(knowledge point)、营养素(nutrient)、同源人工授精(artificial insemination by husband)、异源人工授精(artificial insemination by donor)、生理需要(physiological need)、无性生殖(asexual reproduction)
[单选题]下列哪种免疫途径易形成耐受分离( )
A. 皮下注射
B. 腹腔注射
C. 静脉注射
D. 肌内注射
E. 口服抗原