Gas exchange is the delivery of oxygen from the lungs to the bloodstream, and the elimination of carbon dioxide from the bloodstream to the lungs. It occurs in the lungs between the alveoli and a network of tiny blood vessels called capillaries, which are located in the walls of the alveoli.
Admitted for 180 days â Canadians admitted in âVisitor for Pleasureâ or B-2 status without a B-2 visa in hand are deemed to be admitted for 180 days under current US Customs and Border Protection (CBP) interpretation of the rules.
If you are from Canada, your Tourist Card allows you to stay in Cuba for 90 days. Similarly, if you want to stay in Cuba for more than 90 days, you can extend your Tourist Card for an additional 90 days, at a cost of 25 CUC. The maximum length of stay in Cuba with a Tourist Card for Canadians is 180 days.