​At which one of the following electron transport chain complexes does Antimycin A typically inhibit the respiratory chain?​

Correct option is C

Explanation-

​Antimycin A inhibits the electron transport chain at Complex III (cytochrome bc1 complex). It blocks electron transfer from cytochrome b to cytochrome c1, thereby halting ATP production and respiration.
So, the correct answer is option 3: Complex III 

Incorrect options-

Option 1: Complex I (NADH dehydrogenase)
Antimycin A does not interact with Complex I. Instead, inhibitors like rotenone and piericidin A affect Complex I.

Option 2: Complex II (Succinate dehydrogenase)
Antimycin A has no effect on Complex II. Instead, inhibitors such as thenoyltrifluoroacetone (TTFA) or malonate act on Complex II.

Option 4: Complex IV (Cytochrome c oxidase)
Antimycin A does not inhibit Complex IV. Inhibitors of Complex IV include cyanide, carbon monoxide (CO), and azide.