The pupils are writing .....
the pupils have been writing....
2. what are you doing? I'm surfing..................you have been surfing..............
3. how long have your parents been lived abroad? they have lived ............
4. she is watching tv. granny has watched tv since 2p.m.
5. why is ann crying? ............. you have been crying for half an hour.
6.I'm memorizing. ................. I have been memorizing it since the early morning.