Answer: 2- block of flats [A hundred years ago, we lived in wooden houses. Nowadays, many of us live in blocks of flats.]
3- electric train[A hundred years ago, steam trains were used for transporting goods and people. Nowadays, electric trains serve the same purpose]
4- CD[A hundred years ago, gramophones were used to play music. Nowadays, we use CDs to hear the music we want.]
These are example sentences, you dont have to use them exactly
