Final answer:
The word 'munificent' is the most suitable choice in the sentence, as it means very generous, particularly in relation to money or gifts.
Step-by-step explanation:
In the given sentence, the word that fits bestis 'munificent.' Therefore, the sentence should read: 'The well-known philanthropist gifted a munificent donation, enabling the clinic to build a new surgical wing.' The word 'munificent' means very generous, particularly in reference to money or gifts, making it an appropriate adjective to describe a large donation.
In contrast, 'spontaneous' suggests something done on impulse without planning, 'encouraging' implies providing support or confidence, and 'mosaic' is an image or pattern made from small pieces of colored glass, stone or other materials. None of these options fit as naturally in the context of the sentence.
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