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.
Duration of stay needed is no more than 60 days/per visit for M or L Visa. If you need over 60 days stay, Chinese Consulate will issue only up to 1 year visa. For Canadian passport holder, validity of China visa won't exceed validity of the passport.