Answer:
1- Lily and Sean are not on vacation.
2-Ben isn't hungry now
IF I can sing well enough, I'll join the school chorus.
The IF implies that something is conditional i.e. it may happen, it may not happen (it depends on whether you can sing well enough!)
Hope this helps... :)
1)help your parents
2) do your homework that given by your teachers
3) going to the tuition class