。
Midori ate the most oranges.
Literal
Midori [subject-が] most many orange [object-を] ate.
最も is a formal adverb for 'most, the very X' — a more written-feeling alternative to 一番. 最も多く ('the most in number') is an adverbial phrase modifying the eating. 緑 (Midori) doubles as a common given name and the colour 'green'; here the が-marked subject and the verb make the personal-name reading the natural one. オレンジ is the English loanword for 'orange.'