How many how many Oxygen 2 sensors does a 4 cylinder Nissan Altima have?

A 4-cylinder Nissan Altima typically has two oxygen sensors: one upstream (pre-catalytic converter) and one downstream (post-catalytic converter). The upstream sensor monitors the air-fuel mixture before it enters the catalytic converter, while the downstream sensor checks the efficiency of the catalytic converter. However, it's always best to consult the specific model year and engine type for confirmation, as configurations can vary.