Everyone is studying hard for the exam. Tanaka studies 5 hours a day, Suzuki studies 8. When it comes to Yamada, I hear she's studying so much she's even sacrificing sleep.

"〜に至っては" is used when, after giving a few examples, you single out a particularly extreme one to say "X is especially terrible/amazing." Here, Yamada is presented as the most extreme example compared to Tanaka and Suzuki, so this is the correct answer. "〜ともなると" means "when one reaches the stage/position of X, a certain situation naturally arises," which does not fit the context.

「〜に至っては」は、いくつかの例を挙げた後で、特に極端な例を取り上げて「〜は特にひどい・すごい」と述べるときに使います。ここでは、田中さん、鈴木さんと比べて、山田さんが最も極端な例として挙げられているため、これが正解です。「〜ともなると」は「〜という段階・立場になると、当然〜という状況になる」という意味で、文脈に合いません。