I was reading Matthew 24, and I came across a question.
In Matthew 24, Jesus describes about the last days and the tribulation.
The in verse 34, Jesus says

"Verily I say unto you, This generation shall not pass, till all these things be fulfilled."

There are some churches in this world that believe that the second coming of Jesus has already passed. What do I need to answer to the people that say that the last days and the second coming of Jesus have already passed?
Also, could you explain what this verse means?