It doesn’t matter how steak restaurants attract customers. Like (C), the author doesn’t need to explain why steak restaurants are flourishing. Instead, she needs to explain why the flourishing of these restaurants proves that many people are ignoring the health recommendation.

If anything, the author assumes that people who eat steak do need to follow the advice to reduce high-cholesterol food. People with low cholesterol might be intentionally eating steak, but (B) doesn’t make this attack. Either way, they would still be ignoring the recommendation.

The author doesn’t assume that beef prices dropped or that this caused steak restaurants to be popular. Like (A), she doesn't need to explain why these restaurants are thriving. Instead, she needs to explain how their success shows that many people are ignoring the health advice.

The author never assumes that the decline in beef consumption caused the decline in the restaurant industry or vice versa.

The author draws a conclusion about overall eating habits from one instance of eating high-cholesterol food. She assumes that since people go to steak restaurants, they’re ignoring the advice to avoid high-cholesterol food. But they might follow that advice in their other meals.