Final answer:
In Luke, chapter 21, it will be dreadful for the people living in Jerusalem during the period of great tribulation and the destruction of the city.
Step-by-step explanation:
In Luke, chapter 21, it is mentioned that those days will be dreadful for many people. Specifically, Jesus is referring to the time of great tribulation and the destruction of Jerusalem. In this context, the phrase 'those days' refers to the period of turmoil and suffering that will be experienced by the inhabitants of Jerusalem during the Roman siege in 70 AD. The dreadfulness will primarily affect the people living in Jerusalem at that time.