* * 疼痛的原因是什么？
参考答案：
含接姿势不正确，没有把 * * 、乳晕充分放入嘴内。
John ________ before he got word that the college he chose had accepted him. [ ]
A. held his breath
B. drew a breath
C. took a breath
D. got his breath again
简述超焦距与镜头焦距的关系。
