Final answer:
It is common for safety demos on international flights to be mandatory in English to ensure the widest understanding among passengers, mirroring the marketing trend of using multiple languages to cater to diverse customers.
Step-by-step explanation:
The language in which it is mandatory for a safety demo to be made can vary depending on the country and the airline's regulations. However, in international airlines and contexts, English is commonly required as it is the international language of aviation. This practice ensures that the largest number of passengers understand the safety procedures, similar to how companies use multiple languages for product information and safety warnings to reach a wider audience and support bilingualism.