query will give title of seven most expensive books i.e option C
query is doing nothing just giving title of those books which are cheaper than 6 books atmost.
Like for example you have books in prices range
100,200,300,400,500,600,700,800
now for 100 as there are 7 books which satisfy above condn so condn becomes false so title with book 100 is not included ....rest for all it comes out to be true so it gives output as 200,300,400,500,600,700,800 as output which are nothing but seven most expensive books
So this justifies answer too..!