框架必须足够坚固，以支撑发动机的组装部件。

The frame needs to be strong enough to support the engine ___assembly.

世界各地的各大工厂将自动化机器人集成到它们的装配线上。

Major factories the world over incorporate automated robots into their ___assembly lines.

复杂机械的组装需要精密工具和熟练工人。

The ___assembly of the complex machinery requires precision tools and skilled workers.