• the conjugation of 'to be' with questions and negatives
• the conjugation of 'to have' with questions and negatives
• the conjugation of 'to do' with questions and negatives
• the conjugation of normal verbs (for example: 'to work') with questions and negatives.  (All the normal verbs change in the same way .)
• the Modal Auxiliary Verbs (for example 'can') do not change.

See the Study Programme