A redundancy is when you don't get straight to the point.
It's when you provide useless information.
For example:
Redundant- I have to plan ahead for my trip.
If you are planning, it is already ahead, so saying plan ahead is redundant.
Redundant- I have to wake up at 6 am in the morning for an important meeting.
If it's 6 am, it's already the morning so you don't have to say "in the morning" if you say 6 am.
To fix these, you could say "I'm planning for my trip" or "I have to wake up at 6 am for an important meeting."
This one is a bit tricky but I believe the answer is D.
Skyscrapers are already tall, so you don't have to say "The tall skyscrapers."
So I believe the answer is
D. The tall skyscrapers in New York City maximize the space of a small area.
Hope this helps! :)