Now that she is living in her own flat, (a)/ she cleans the windows (b)/ twice a week in the summer and once a week in the winter.(c)/ No error (d)

Answer

c

Explanation

The senson e.g., summer, winter, etc are abstract nouns. So, articles are not used with them. So, we would remove 'the, before 'summer' and 'winter' and change them to 'summers' and 'winters'.