【简答题】骨料在混凝土中起 作用,能够传递应力,抑制收缩,防止开裂,使混凝土具有更好的 。
【简答题】用白光垂直照射一厚度为 400 nm 、折射率为 1.50 的空气中的薄膜表面时,反射光中被相干加强 的可见光波长为 nm
【单选题】Why does Sam want to target the 46-55 age group?
A.
They have more buying power.
B.
They are vey health conscious.
C.
They tend to enjoy sports more.