It took a long time for people to realize where this disease came from. For hundreds of years, they thought it was due to dirty air, especially near swamps. In fact, it is caused by the bite of an infected mosquito. Not all mosquitoes carry this disease, and some mosquitoes actually get it from biting an infected person.
Which sentence from the passage contains the central idea?
It took a long time for people to realize where this disease came from.
For hundreds of years, they thought it was due to dirty air, especially near swamps.
In fact, it is caused by the bite of an infected mosquito.
Not all mosquitoes carry this disease, and some mosquitoes actually get it from biting an infected person.
