1.the oldest part of the Great wall has a history of over 25

1.the oldest part of the Great wall has a history of over 25 centuries.译这个句子.part 是什么
意思?
2.most traffic lights along the road don't work after the typhoon.so make sure no cars are coming when you cross it.译这个句子,make sure
3.A snake always sleeps( for months ) in cold winter.
4.what are you going to be when you grow up?() teacher like you.
A a B the C an D/