Final answer:
The form required by the UK and completed by all crew members is the Passenger Locator Form. It is used to track and prevent the spread of diseases by collecting travel and contact details of the crew. So, the correct answer is Option 4: Passenger locator form.
Step-by-step explanation:
The form required by the UK and completed by all crew members is the option 4: Passenger Locator Form. This form is part of the health measures implemented to track and prevent the spread of diseases.
Upon entering the UK, all crew members on air, sea, or rail transport are required to fill out this form to provide travel and contact details. It allows the UK government to contact the crew members if one or more passengers on a voyage tested positive for a contagious disease or if they need to self-isolate upon arrival.
This is different from a customs declaration, landing card, or immigration form, which serve different purposes such as declaring goods, recording entry into a country, or processing individuals for immigration clearance.