1. came / were singing
2.joined
3.were writing
4.leaved
5.continued
ex 4: 
1.china is the most crowded country in the world
2.Married women can be encouraged to pursue a career of their preference.
3.John is the tallest boy in our class
4.no boy is taller than Nam in my class
5.Nga is the most friendliest student in her class