Определить форму инфинитива. Indefinite или Perfect? И как вообще их различать. Заранее БОЛЬШОЕ спасибо. 1. Witnesses for the prosecution may be cross-examined. 2. The House of Lords has no power to throw out a bill relating to money. 3. The defendant preferred to make a statement through his solicitor. 4. The object of punishment is to reform and educate the guilty person. 5. The judge must have discharged one of the jurors. 6. He went to Oxford to study law.

Во 2 и в 5 предложениях perfect. Present perfect можно найти по форме have или has +глагол 3 формы