a) A DataFrame is like a fixed-size dict in that you can get and set values by index label
b) Series can be be passed into most NumPy methods expecting an ndarray

c) A key difference between Series and ndarray is that operations between Series automatically align the data based on label
d) None of the mentioned

Answer: a
Explanation: A Series is like a fixed-size dict in that you can get and set values by index label.