What inference can you make about the effect of tides on health in jamestown

Jamestown was situated on a site that was too secluded for agriculture, in fact, the entire island was isolated because it was swamp-like and infested with mosquitoes and the only water came from tidal rivers. This water was unsafe to drink, which could cause health problems such as cholera, typhoid or dysentery. 

was found at b)south carolina

c. troops marched forward in close formation against newer, more accurate weapons