The three examples of sentences which are not statements are as follows
(i) He is a doctor
It is not evident from the sentence as to whom 'he' is referred to Therefore it is not a statement
(ii) Geometry is difficult
This is not a statement because for some people geometry can be easy and for some
others it can be difficult
(iii) Where is she going?
This is a question which also contains 'she' and it is not evident as to who 'she ' is
Hence it is not a statement