The correct answer is C. Error involving numbers
Step-by-step explanation:
According to grammar and style manuals, small numbers should be spelled or written using letters and big numbers should be written using numerals. About this is considered numbers under 10 should be spelled although some manuals established numbers under 100 can be spelled. Besides this, if the number is the first element in a sentence it should be spelled in all cases except if the number is a year. This means in the case of the sentence "3 days of our holiday are left to enjoy" the writer should have written 3 as "three" and thus, in this sentence there is an error involving numbers.