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trinidadParis and Montreal are two French-speaking cities.
No.
The whole country of Madagascar has French-speaking populations, usually the highly educated. Antananarivo, the capital city, like other Malagasy cities has a french speaking population.
Paris and Bordeux
In Quebec, French is the official language and is predominantly spoken in many cities. The largest city, Montreal, has a significant French-speaking population, as does the provincial capital, Quebec City. Other cities such as Laval, Gatineau, and Trois-Rivières also have French-speaking communities, contributing to the province's strong francophone culture. Overall, French is widely used throughout the province, making it a central aspect of daily life in these urban areas.
Well I imagine that French would be a minority language but there are French speaking people in various parts of Louisiana - Eunice, Bâton Rouge, New Orléans, Big Mamou. There are also associations of people of French origin in Maine but I'm not sure that they speak French.
No, London is not the 5th largest French-speaking city in Europe. Paris, Brussels, and Geneva are among the cities with larger French-speaking populations than London.
Quebec, Toronto, Paris, Winnipeg, Switzerland, Belguim
There are 29 countries worldwide where French is an official language.
Paris and Djibouti are both capital cities, both their countries' largest cities, both primarily French-speaking (Djibouti was founded by the French in 1888).
The largest city is Zürich (German speaking) then in order Geneva (French speaking, Genève in French), Basel (German) Bern (the capital, German) Lausanne (French)
pretty much all of Canada, the main city is Montreal