intangible non current assets

please, help me ,Sir

question:
Which of the following items(that all generate future economic benefits,and whose costs can be measured reliably), is an intangible non-current asset?

1 Computer hardware owned by a business
2 Operating software that operates the computer hardware in (1)
3 a patent bought by a business
4 An extension to an office building owned by a business

the answer is only 3??
because operating software is tangible.

question belongs to Revision&kit(page 47,question 9.14)
but l suppose that correct variant have not been given in “the answers” section..