放射治疗的放射源有3类,即()、()和()。
参考答案:放射线核素;X线;加速器
Students in our school are encouraged to________more activities after class in order to broaden their
knowledge.[ ]
A.attend
B.join
C.take part
D.participate in
产成品A单身的材料品号B的“投料间距”为2,表示()。
A.开工前2天则要投入品号B
B.开工后2天则要投入品号B
C.完工前2天则要投入品号B
D.完工后2天则要投入品号B