This exercise challenges students to select the correct prefix, "un-" or "dis-", to negate or reverse the meaning of twenty common root words.

Let’s go through each word one by one and decide whether to add un- or dis- to make a new, correct word.

We’ll think about what the original word means, and then what the opposite or negative version would be — that’s what prefixes like “un-” and “dis-” do. They change the meaning to its opposite or show something is not happening.

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1. load → If you *unload*, you take things off. So: unload

2. happy → The opposite of happy is unhappy. So: unhappy

3. comfort → To make someone uncomfortable = remove comfort. So: uncomfortable? Wait — but we’re adding prefix to “comfort”, not “comfortable”. Actually, “discomfort” is the noun/verb form. But in this context, since it says “add prefix to root word”, and “comfort” can become “discomfort” (meaning lack of comfort), let’s check common usage.
Actually, both “uncomfort” and “discomfort” exist? No — “uncomfort” isn’t standard. It’s discomfort. So: discomfort

Wait — hold on! Let me double-check. In elementary worksheets, they often expect “uncomfortable” for #15, so maybe for #3 “comfort”, they want “discomfort”? But “discomfort” is more formal. Alternatively, maybe they accept “uncomfort” — but that’s not real. Hmm.

Actually, looking at standard English:

- “Comfort” → “Discomfort” (correct)
- “Comfortable” → “Uncomfortable” (correct)

So for #3: discomfort

But wait — some curricula might simplify. Let’s look ahead — #15 is “comfortable”, which will be “uncomfortable”. So yes, #3 should be “discomfort”.

4. continue → Stop continuing = discontinue. So: discontinue

5. friendly → Not friendly = unfriendly. So: unfriendly

6. allow → Not allow = disallow. So: disallow

7. fair → Not fair = unfair. So: unfair

8. obey → Not obey = disobey. So: disobey

9. respect → Not respect = disrespect. So: disrespect

10. tie → Untie means to loosen a knot. So: untie

11. agree → Disagree means not agree. So: disagree

12. trust → Distrust means not trust. So: distrust

13. order → Disorder means chaos, no order. So: disorder

14. ripe → Unripe means not ripe (like green fruit). So: unripe

15. comfortable → Uncomfortable means not comfortable. So: uncomfortable

16. honest → Dishonest means not honest. So: dishonest

17. pleasant → Unpleasant means not pleasant. So: unpleasant

18. zip → Unzip means open a zipper. So: unzip

19. known → Unknown means not known. So: unknown

20. sure → Unsure means not sure. So: unsure

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Now let’s list them all clearly with answers:

1. load → unload
2. happy → unhappy
3. comfort → discomfort
4. continue → discontinue
5. friendly → unfriendly
6. allow → disallow
7. fair → unfair
8. obey → disobey
9. respect → disrespect
10. tie → untie
11. agree → disagree
12. trust → distrust
13. order → disorder
14. ripe → unripe
15. comfortable → uncomfortable
16. honest → dishonest
17. pleasant → unpleasant
18. zip → unzip
19. known → unknown
20. sure → unsure

I’ve checked each one against standard English usage. Some words like “discomfort” vs “uncomfort” — only “discomfort” is correct. Similarly, “discontinue”, “disallow”, etc., are standard.

Final Answer:
1. unload
2. unhappy
3. discomfort
4. discontinue
5. unfriendly
6. disallow
7. unfair
8. disobey
9. disrespect
10. untie
11. disagree
12. distrust
13. disorder
14. unripe
15. uncomfortable
16. dishonest
17. unpleasant
18. unzip
19. unknown
20. unsure