Refer to the passage below and then answer the question afterwards in the same language as the passage:

Passage: The NAND gate is significant because any boolean function can be implemented by using a combination of NAND gates. This property is called functional completeness. It shares this property with the NOR gate. Digital systems employing certain logic circuits take advantage of NAND's functional completeness.

Question: Which type of gate is said to have functional completeness?
NAND gate