Which two reasons could have caused these wait events?

While reviewing the Top 5 Timed Events section in the Automatic Workload Repository report, you
notice that the db file scattered read and db file sequential read events appear in the list. Which
two reasons could have caused these wait events? (Choose two.)

A.
SQL statements performing frequent full table scans

B.
tablespaces using manual segment space management

C.
SQL statements performing frequent fast full index scans

D.
excessive writes due to an aggressive checkpointing policy