D. Fill in the blanks with an appropriate relative pronoun or adverb:
[填空题]
(1) Deserts are found ______ rain never falls or falls in only a few weeks' time for a whole year.
[填空题]
(2) That was the proposal she put forward at the board meeting ____ it was turned down by all the other members.
[填空题]
(3) The treatment, _____ is being tried by doctors at these hospitals, has proved to be effective for patients.
[填空题]
(4) Mrs Taylor, _____ came on holiday with us, is now in Shanghai.