B)Investing in the new library is investing in our children's future.
Step-by-step explanation:
Investing in a library to make the future of children better looks to be the logical statement which is not the case for any other statement here. Libraries help in the inculcation of a habit of reading in young children which facilitates growth and learning in them.
The other statements cannot be logical.
No library can make a city a great one as it is not one of the parameters of a great city.
Investing in a library is not throwing money either as it is a great service to society.
The last statement is unclear and without much to go for reference.