Final answer:
A mixed sequence of letters and numbers is best represented by a String data type, as it can contain a versatile combination of characters.
Step-by-step explanation:
The data type represented by a mixed sequence of letters and numbers is a String. This is because a String can hold a sequence of characters, including both letters and digits, as well as special characters and punctuation. If you were to analyze types of data, such as the number of pairs of shoes you own or the weights of sumo wrestlers, the appropriate data type would be quantitative and more specifically, discrete quantitative data, because they represent counts of items or measurements respectively. However, for a mixed sequence of letters and numbers, which doesn't represent a countable quantity or a true/false condition, but rather a sequence of alphanumeric characters, the correct data type is a String (Option C).