Answer:
Oxidative phosphorylation that generates most of the ATP is blocked, and oxygen cannot accept the electrons from NADH.
Explanation: Sorry this is late and may be wrong but it is my best guess and here is why:
Potassium cyanide blocks the ETC where the majority of ATP is produced. The ETC is a oxidative phosphorylation process where oxygen is needed as the final electron acceptor of NADH.
The first answer can be eleminated because oxidative phosphorylation produces the most ATP.
The second answer can be eleminated because chemiosmosis does not generate ALL the ATP during cellular respiration, but does produce most of it. Still they worded it as an "all or nothing" type of question so I don't think it is correct.
The fourth answer may not be correct because NAD does not pass on an electron to NADH. Instead, NADH donstes electrons to the ETC and is then turned into NAD. So the process listed is technically backwords.
Sorry I can't be sure about the answer but this is how I broke it down.
