金属材料的收缩性会使铸件产生锁孔、疏松、内应力、变形和开裂等缺陷,收缩率应越小越好。
参考答案:对
I have no idea ___.
A.that she has come
B.what she has come
C.that she comes
D.what she came
患者,男,主诉右眼急性视力下降3天,眼底检查见视网膜广泛出血,视网膜静脉扩张迂曲,最先考虑的是()
A.视网膜中央静脉阻塞
B.视网膜中央动脉阻塞
C.原田病
D.球后视神经炎
E.视网膜脱离