All the following statements about data streams are correct except:
a. With continuous queries of data streams, the queries are more static while the data is more dynamic.
b. Every query issued over a data stream should have a window defined becasue the data stream is infinite and unbounded.
c. B+ tree indexing that we learned, where each node corresponds to a disk block, is not suitable for data streams.
d. Map reduce can be used for data streams.