Answer:
Oxygen in a container can be made to be at a high pressure through a process called compression. In this process, the oxygen is forced into a smaller volume, which increases the pressure. This can be done using a compressor, which is a machine that uses a piston or other device to compress the oxygen. The compressed oxygen is then stored in a container, such as a cylinder, at high pressure until it is ready to be used. It is important to handle compressed oxygen with care, as it can be dangerous if not handled properly.