具有内皮绒毛膜胎盘(环状胎盘)的动物是() ["A、马","B、牛","C、羊","D、猪","E、犬"]
整体式型腔与局部镶拼式型腔有何特点?
浇口作用是什么?常用的浇口类型有哪几种?
猫前肢采血的静脉是() ["A、腋静脉","B、头静脉","C、臂静脉","D、隐静脉","E、正中静脉"]
心脏的传导系统包括窦房结、房室结、房室束和() ["A、神经纤维","B、神经原纤维","C、肌原纤维","D、胶原纤维","E、普金野纤维"]
冲裁模试冲时,冲裁件的毛刺较大的原因是什么?说明解决方法。