In an informal style this and that are often used with adjectives and adverbs in the same was as so.
- I didn’t realize that it was going to be this hard. (= I didn’t realize that it was going to be so hard.)
- If he is that clever, why isn’t he successful?
- If it goes on raining this hard, we will have to swim to work.
‘Not all that’ can mean ‘not very’.
- ‘How was the film?’ ‘Not all that bad.’
On the telephone
On the telephone, British people use this to identify themselves, and that to ask about the hearer’s identity.
- ‘Hello. This is Jane. Is that Stella?’
In American English, this can also be used to ask about the hearer’s identity.
- Who is this / that? (US)
- Who is that? (GB)
Difference between this / that and it
This, that and it can all be used to refer back to things that have already been mentioned. There is little difference of meaning.’ Note that this and that are more emphatic than it.
- So she decided to marry her boss who was 20 years older than her. It upset her mother quite a bit.
- So she decided to marry her boss who was 20 years older than her. This / that upset her mother quite a bit.
It can only be used to refer to things which have already been talked about. To talk about things that have not yet been mentioned, we use this.