Final answer:
The sentence is capitalized correctly, with 'Mark' being the only word that needs to be capitalized besides the first letter of the first word. 'Cheddar' and 'bacon' are common nouns and do not require capitalization.
Step-by-step explanation:
The sentence 'Mark made a recipe for grilled cheese sandwiches that used cheddar and bacon.' is capitalized properly. In English grammar, the first word of a sentence should always be capitalized, which is correctly done with 'Mark.' Additionally, proper nouns are capitalized, but 'cheddar' and 'bacon' are not proper nouns; they are common nouns referring to types of food. Since this sentence does not contain any proper nouns or titles that would require further capitalization, all the words are capitalized appropriately according to standard sentence capitalization rules.