Regarding single row functions in Oracle Database 12c:
* C. CEIL: can be used for positive and negative numbers. This is true. The CEIL function rounds a number up to the nearest integer, and it works for both positive and negative values.
* D. TRUNC: can be used with NUMBER and DATE values. This is correct. The TRUNC function can truncate numbers or dates to a specified precision.
Options A, B, and E are incorrect:
* A is incorrect because CONCAT function typically concatenates two strings; to concatenate more, you must nest CONCAT calls or use the || operator.
* B is incorrect because FLOOR returns the largest integer less than or equal to the specified number, not greater.
* E is incorrect because MOD returns the remainder of a division operation, not the quotient.