Which of the following is not a sentence ? a. winding up the pole b. the ferret has a silly look on its face c. i really do like spinach d. the men’s bathroom is out of order

A sentence refers to the pair of words which is complete in itself. In other words, a sentence contains a subject and a predicate or it may contain a main clause and one or more subordinate clauses to convey a command, exclamation, question or statement.

In the following statements, the sentences have subject and predicate,

B. The ferret has a silly look on its face.

'The ferret'- subject

'has a silly look on its face'- predicate

C. I really do like spinach.

'I' - subject

'really do like spinach'- predicate

D. The men’s bathroom is out of order.

'The men’s bathroom'- subject

'is out of order'- predicate

Hence, the sentence 'Winding up the pole' doesn't have a subject that's why it is not a sentence.