The correct option is C length of the room wall
The lengths of the cupboard and the room wall are being compared. The underlined phrase does not indicate the length of the room wall. This needs to be corrected, option A is incorrect. The grammatical structure of option B is different from the phrase 'length of the cupboard', hence it's incorrect. Since the sentence mentions the length as a comparison, 'measurement' is vague according to the specified length, hence C is incorrect. The last option has the same grammatical structure as the first phrase in the sentence, it's the correct option.