Past Simple and Past Continuous

When my dad came home I was having dinner.

When my dad was coming home I was having dinner.

When my dad came home I had dinner.

When my dad was coming home I had dinner.

What were they doing when you saw them?

What they were doing when you saw them?

What did they do when you saw them?

What were they doing when you were seeing them?

While my brother was sleeping, my mother was preparing dinner.

While my brother was sleeping, my mother prepare dinner.

While my brother was sleeping, my mother prepared dinner.

While my brother slept, my mother was preparing dinner.

Her son fell when he was climbing the tree.

Her son fall when he was climbing the tree.

Her son fell when he climbed the tree.

Her son was falling when he was climbing the tree.

It was snowing when I left home.

It snowed when I left home.

It was snowing while I was leaving home.

It was snowing when I leaved home.

When the teacher came into the classroom, all the pupils were sitting at their desks.

When the teacher was coming into the classroom, all the pupils were sitting at their desks.

When the teacher was coming into the classroom, all the pupils sat at their desks.