Final answer:
The result of the expression df['a'] > 10 cannot be determined without the actual data in the dataframe. It returns a Boolean series where each value is True or False depending on if the condition is met.
Step-by-step explanation:
The expression df['a'] > 10 is used in the context of programming, specifically in data manipulation with libraries such as pandas in Python. When this expression is evaluated, it checks whether each element in the 'a' column of the dataframe 'df' is greater than 10. The result is a Boolean series where each value corresponds to either True or False based on whether the condition is met for the respective element. Therefore, the correct answer is 3) Cannot be determined from the given information because without the actual data present in the dataframe, we cannot ascertain the individual truth values that will result from the expression.