Вопрос:

49. Paul didn't like decorating, so he got a professional decorator __________ his flat for him. A) designing; B) design; C) she designed; D) to design.

Ответ:

Paul didn't like decorating, so he got a professional decorator to design his flat for him.

После конструкции get someone используется инфинитив с to: get someone to do something.

Ответ: D) to design.