那座旧桥很脆弱，可能无法支撑重型车辆。

The old bridge is ___weak and may not support heavy vehicles.

那把椅子有一条腿不结实，所以如果你坐上去可能会断。

That chair has a ___weak leg, so it might break if you sit on it.

地震后，建筑物的结构变得脆弱。

The structure of the building is ___weak after the earthquake.