不牢固的
5.It seems catastrophism is an unstable theory with serious problems concerning the magnitude of the event and its repercussions.
6.The learning of the bright student who acquires knowledge with ease and speed is felt to be unstable; easy come, easy go.
7.The multitude surged towards them, and they already saw the frail wooden balustrade that formed the only barrier between them and the crowd bulge and give way under the pressure from without.
9.The surveyor maintains that the damage was due to insecure packing and not to any unduly rough handing.

