Pick out the incorrectly spelt word :

To find the incorrectly spelt word, check each option for correct spelling. Option A: Microscope – The spelling is correct. It has 'mi', 'cro', 'scope' with 'sc' in the middle. Option B: Opaque – The spelling is correct. It has 'op' and 'aque' with 'q' and 'e' at the end. Option C: Mosaice – This is incorrect. The correct spelling is 'Mosaic'. The word ends with 'c' and 'e', not 'i' and 'e'. Option D: Monarchy – The spelling is correct. It has 'mon' and 'archy' with 'n' and 'a' in the right order. Thus, the incorrectly spelt word is 'Mosaice'.