Identify presupposition-triggers

Decide for each of the following pairs which sentence contains a presupposition. Identify the presupposition-trigger.

a) Sally thought she was in love with John. – Sally realized she was in love with John. (:vips 7582:) (:vips 7781:)

b) John has stopped doing linguistics. – John has tried doing linguistics. (:vips 7583:) (:vips 7782:)