Final answer:
The London convention on the prevention of marine pollution is an international agreement that applies to all countries that signed it.
Step-by-step explanation:
The international agreement that applies to all countries that signed it is the London convention on the prevention of marine pollution. This agreement aims to reduce and prevent pollution from ships and other marine activities in order to protect the marine environment. It establishes guidelines and regulations for the disposal of wastes and other harmful substances to prevent marine pollution.