Answer:
keywords are important for searching for the exact term you are looking for by using the most specific word possible, and boolean operators can help you expand or restrict your search, such as searching for "people named bob AND people named george"
The "middle ages" are anything between the collapse of Rome (400 AD) to its re-emergence in Rennaissance Italy (1400). Rennaissance means "rebirth". The "dark ages" are the period in the middle ages which were relatively undocumented. This would definitely include 400 AD to 700 AD, and some extend it to 900 AD.
Answer:
App that reminds you to drink water
Explanation:
A lot of people are dehydrated because they don't remeber to drink water
