Explanation:
IDS*2, TS+IYM and IDS+IYM are valid new date and time data types. Incorrect Answer:
3: You cannot subtract timestamps.
4: Also it is not possible to subtract timestamp from the interval day to second.
Reference:
OCP Oracle 9i Database: New Features for Administrators, Daniel Benjamin, p. 266-271
Chapter 5: Language Enhancements
Oracle 9i New Features, Robert Freeman, p. 132-135
Chapter 5: Miscellaneous Oracle 9i Features and Enhancements

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