【推荐1】Stephen Hawking is an internationally-recognized theoretical _______(physical),and is the Lucasian Professor of Mathematics at Cambridge University. （所给词的适当形式填空）

【推荐2】Most of the visitors are ________ by the ________ town, which is a famous tourist ________. (attract) (用所给词的适当形式填空)

【推荐3】I would like to do some ________ work in the exhibition. So I am writing this letter asking to be a ________. (voluntary) (所给词的适当形式填空)