1 a) Don't forget to tell Kristen about the beach party tonight.

b) I'll never forget going to Australia last summer.

The difference in meaning:

In sentence (a), "forget to tell" implies that there is an action (telling Kristen) that needs to be remembered or not forgotten in the future.

In sentence (b), "never forget going" implies that the speaker will always remember the experience of going to Australia last summer.

2 a) Stop playing that music! It's really annoying!

b) Let's stop to buy something to eat. I'm so hungry.

The difference in meaning:

In sentence (a), "stop playing" is a command to cease the ongoing action of playing music.

In sentence (b), "stop to buy" suggests stopping one action (e.g., walking) in order to perform another action (buying something to eat).

3 a) Try drinking some mint tea. It's good for your stomach.

b) Try being here on time for the meeting.

The difference in meaning:

In sentence (a), "try drinking" suggests trying the action of drinking mint tea to see if it has a beneficial effect.

In sentence (b), "try being" suggests making an effort to be present on time for the meeting.

4 a) I regret inviting Angie to Luke's birthday party.

b) I regret to inform you that your application was not successful.

The difference in meaning:

In sentence (a), "regret inviting" implies feeling sorry or remorseful about the action of inviting Angie to the party.

In sentence (b), "regret to inform" implies feeling sorry or reluctant about the necessity of conveying unpleasant information.

5 a) Remember to lock the door before you go.

b) I am sorry but I don't remember meeting you at Mike's party.

The difference in meaning:

In sentence (a), "remember to lock" suggests remembering or not forgetting to perform the action of locking the door.

In sentence (b), "don't remember meeting" suggests not recalling or not having a memory of the action of meeting at Mike's party.