3. Circle the correct item. 1) Professor Scott was reading some papers while /as his assistant came into the laboratory. 2) Mary was cooking a vegetable salad while/when she found out that there wasn't any salt in the box. 3) While/As Lisa was writing a test, her friend was waiting for her outdoors. 4) Sheila was weeding cucumbers while /when her younger sister was picking strawberries. 5) While/When Charlie entered the classroom, his teacher was explaining something to his classmates. 6) While/As two women were talking, their children were playing badminton on the playground. 7) Sam was repairing his bike in the backyard while/as he heard a cry for help. 8) While/As I was doing the washing-up, I broke a plate.

3. Circle the correct item.
1) Professor Scott was reading some papers while/as his assistant came into the laboratory.
- The correct item to circle is "while".
- "While" is used to show that two actions were happening at the same time, but independently of each other. In this sentence, the professor was reading papers at the same time as his assistant entered the laboratory.

2) Mary was cooking a vegetable salad while/when she found out that there wasn't any salt in the box.
- The correct item to circle is "when".
- "When" is used to show that one action happened immediately after another. In this sentence, Mary found out that there was no salt after she started cooking the salad.

3) While/As Lisa was writing a test, her friend was waiting for her outdoors.
- The correct item to circle is "while".
- "While" is used to show that two actions were happening at the same time, but independently of each other. In this sentence, Lisa was writing a test while her friend waited for her outdoors.

4) Sheila was weeding cucumbers while/when her younger sister was picking strawberries.
- The correct item to circle is "while".
- "While" is used to show that two actions were happening at the same time, but independently of each other. In this sentence, Sheila was weeding cucumbers while her younger sister was picking strawberries.

5) While/When Charlie entered the classroom, his teacher was explaining something to his classmates.
- The correct item to circle is "while".
- "While" is used to show that two actions were happening at the same time, but independently of each other. In this sentence, Charlie entered the classroom while his teacher was explaining something to his classmates.

6) While/As two women were talking, their children were playing badminton on the playground.
- The correct item to circle is "while".
- "While" is used to show that two actions were happening at the same time, but independently of each other. In this sentence, two women were talking while their children were playing badminton on the playground.

7) Sam was repairing his bike in the backyard while/as he heard a cry for help.
- The correct item to circle is "as".
- "As" is used to show that one action happened at the exact moment or just after another action started. In this sentence, Sam heard a cry for help while he was repairing his bike.

8) While/As I was doing the washing-up, I broke a plate.
- The correct item to circle is "while".
- "While" is used to show that two actions were happening at the same time, but independently of each other. In this sentence, the speaker was doing the washing-up while they broke a plate.