PT 41 S3 Q20

On some hot days the smog in Hillview reaches unsafe levels, and on some ... ...

The reasoning in the argument is flawed in that the argument
(A) mistakes a condition that sometimes accompanies unsafe levels of smog for a condition that necessarily accompanies unsafe levels of smog
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Practice Set: "Flawed Reasoning" Questions, Set 2 - Conditionals