E. Underline the correct form. 1. Then/when we watch a film at the cinema, we eat chocolates and popcorn. 2. They have dinner when/before he leaves for work. 3. Mary cleans her room on Sundays. After that/And she plays computer games. 4. On Saturdays we have lunch and then/before we go shopping. 5. They always leave out food for the dog before/and they leave the house.​

1. Then/when we watch a film at the cinema, we eat chocolates and popcorn.
The correct form is "when." We use the word "when" to indicate that two actions are happening at the same time. In this sentence, the actions of watching a film and eating chocolates and popcorn are happening simultaneously.

2. They have dinner when/before he leaves for work.
The correct form is "before." We use the word "before" to indicate that one action happens prior to another. In this sentence, the action of having dinner occurs before the action of him leaving for work.

3. Mary cleans her room on Sundays. After that/And she plays computer games.
The correct form is "after that." We use the phrase "after that" to show that one action occurs immediately following another. In this sentence, the action of playing computer games happens after the action of cleaning her room.

4. On Saturdays we have lunch and then/before we go shopping.
The correct form is "before." Similar to the second sentence, we use the word "before" to indicate that one action happens prior to another. In this sentence, the action of going shopping occurs after the action of having lunch.

5. They always leave out food for the dog before/and they leave the house.
The correct form is "before." Again, we use the word "before" to show that one action happens prior to another. In this sentence, the action of leaving food for the dog occurs before the action of leaving the house.

I hope this explanation helps you understand the correct forms and their meanings in these sentences! Let me know if you have any further questions.