Up till now, full use of this theory has been ________ in building large ocean-going ships.
29. That's all for the party. Let's _____.
28. They ____ friends since they met in Shanghai ten years ago.
27. When he heard the news, his heart ______ very fast.
26. The old woman could not _____ the terrible noise, and she had to close the door and windows.
25. --- We could have walked to the station. It was so near. --- Yes. A taxi ____ at all necessary.