答案:C
— I come all the way to say "Thank you" and we ____ it without you.
— Think nothing of it. [ ]
A. should have done
B. mustn't have done
C. couldn't have done
D. needn't have done
碱活性骨料是指在一定条件下会与混凝土中的()发生化学反应,导致混凝土结构产生()、(开裂)、甚至()的骨料。