The correct option is
C Banish
All the given words are verbs. 'Engage' means 'occupy or attract someone's attention'. Eg: 'My mind is engaged in solving this problem' means the same as 'My mind is occupied with solving this problem'. Hence, 'engage' has the same meaning as 'occupy'.
'Engage' also means 'to hire someone'. The word, 'retain' also means 'to hire the services of someone'. Eg: The below three sentences means the same:
i) 'We have engaged a detective'.
ii) 'We have hired a detective'.
iii) 'We have retained the services of a detective'.
Hence, the words, 'engage', 'hire' and 'retain' have a similar meaning.
'Engage' also mean 'secure something for use'. 'Reserve' also means the same. Eg: 'I have engaged a room' means the same as 'I have reserved a room'.
Options A, B and C are incorrect as they share their meanings with the word, 'engage'.
'Banish' means 'to send someone away, especially from their country, and not allow them to come back'. Its meaning is different from that of the other words. Hence, option D is the correct answer.