English grammar worksheet focusing on the correct usage of "saw" and "seen" with exercises for students.

Explanation:
We need to choose between saw and seen for each sentence. Here's how to decide:

- Saw is the simple past tense of *see*. Use it when the action happened at a specific time in the past, and there’s no helping verb like *have*, *has*, or *had*.
- Example: *I saw the movie yesterday.*

- Seen is the past participle. It’s used with helping verbs: *have*, *has*, or *had* (e.g., *I have seen*, *She has seen*, *They had seen*). Also, *seen* is used after *be* verbs in passive constructions (like *was seen*), but that’s less common here.

Let’s go through each sentence:

1. Mark has ___ the movie several times.
→ “has” is a helping verb → needs past participle → seen

2. I was ___ entering the school.
→ “was” is a form of *be*; this is likely a typo or awkward phrasing, but standard usage would be *I saw myself entering* or *I was seeing…* — however, in basic grammar exercises, if it says “I was ___ entering”, the only grammatical option with *see* is not natural. But looking at context, this is probably meant to be saw? Wait—no. Let’s re-read: “I was ___ entering the school.” That structure usually goes with *watching* or *observing*, but with *see*, the correct form would be seeing (present participle), but that’s not an option. Since only *saw* and *seen* are given, and *was seen* would be passive (“I was seen entering…” meaning someone saw me), but that changes meaning. However, in many worksheets like this, #2 is intended to be saw, but that would be *I saw myself entering* — not matching “was”. Let’s hold and check others.

Actually, let’s look at the instruction again: “Circle the word that best completes the sentence.” And only two choices: *saw* / *seen*.

So for #2: *I was ___ entering the school.*
→ If we pick *saw*, it becomes *I was saw entering* → incorrect (double verb).
→ If we pick *seen*, it becomes *I was seen entering* → grammatical passive: someone saw me entering. That makes sense. So seen.

3. The cat ___ the mouse.
→ No helper verb → simple past → saw

4. The children ___ the teacher coming down the hall.
→ No helper verb → simple past (past event) → saw

5. You ___ it too, didn’t you?
→ This is a tag question. The main verb must match the auxiliary in the tag (*didn’t you?* = *did not you*), so the main verb is simple past → saw

6. You ___ the zebras in the field.
→ No helper verb → simple past (unless context implies experience, but no *have*), so saw

7. I ___ the tennis match.
→ No helper verb → simple past (assuming a completed past event) → saw

8. They have ___ the elephants already.
→ “have” + past participle = seen

9. He has ___ his cousin leaving this morning.
→ “has” → needs past participle = seen

10. Mark has ___ three football games this week.
→ “has” → seen

11. We ___ our friends on the playground.
→ No helper verb → simple past = saw

12. She ___ the snowman just before it melted.
→ No helper verb, specific past time (*just before...*) → saw

13. They ___ just leaving before the accident.
→ Again, no helper verb, and *just* suggests immediate past → saw

14. My dog ___ a squirrel and took off after it.
→ Two past actions joined by *and* → both simple past → saw

15. Life as we ___ it was changed forever.
→ This is a relative clause: *as we ___ it* → “we have seen it” is idiomatic, but here it’s describing life *in the way we experienced it*. Standard phrase: *as we have seen it* → but the sentence doesn’t have *have*. Wait — structure: “Life as we saw it…” is correct for simple past description (e.g., *the world as we knew it*). Yes — this is a fixed expression using simple past. So saw.

Now double-check tricky ones:

#2: *I was seen entering* = passive, meaning others saw me. Acceptable. In school worksheets, this is often the intended answer.

#6: Could it be *have seen*? But no “have” in sentence, so no.

Let’s list all answers clearly:

1. seen
2. seen
3. saw
4. saw
5. saw
6. saw
7. saw
8. seen
9. seen
10. seen
11. saw
12. saw
13. saw
14. saw
15. saw

That’s consistent.

Final Answer:
1. seen
2. seen
3. saw
4. saw
5. saw
6. saw
7. saw
8. seen
9. seen
10. seen
11. saw
12. saw
13. saw
14. saw
15. saw