【单选题】UNIT 1 PAGE 14 CONVERSATION .2
【简答题】A.subway B.Thursday C.nowadays D.x-ray
【单选题】UNIT 1 PAGE 14 CONVERSATION .3
【简答题】普通混凝土的主要组成材料有哪些?各组成材料在硬化前后的作用如何?
【单选题】In connection with x-ray emission the symbol Kα refers to:
A.
an alpha particle radiation
B.
x-ray radiation from potassium
C.
x-ray radiation associated with an electron going from n = 2 to n = 1
D.
x-ray radiation associated with an electron going from n = 3 to n = 1
【单选题】UNIT 1 PAGE 14 CONVERSATION .1
【单选题】Frequent exposure to X-ray is harmful, so the use of X-ray should be limited to occasions when______.
【单选题】UNIT 1 PAGE 14 CONVERSATION .4