8.91 referring to things

When you are referring to a thing or group of things, you use 'which' or 'that' as the subject of a defining clause.

• ...pasta which came from Milan.
• In fact there are strategies which are much more reliable.
• There are a lot of things that are wrong.

You use 'which' or 'that' as the object of a defining clause, or you do not use a pronoun.

• ...shells which my sister had collected.
• ...the oxygen that it needs.
• ...one of the things I'll never forget.

After 'much' or 'all', you use 'that'. You do not use 'which'.

• There was not much that the military men could do.
• Happiness is all that matters.