---
title: "English C-Test B2: How vaccines are tested · C-Test Prep"
description: "Free English C-Test at B2 level: \"How vaccines are tested\", 25 gaps to fill in and check online, with the answer and an explanation for every gap."
canonical: https://ctestprep.de/en/c-test-english-exercises/b2-how-vaccines-are-tested
last_updated: 2026-10-31
---

# English C-Test B2: How vaccines are tested

An English C-Test at B2 level: longer sentences with clauses and the passive, topics from study and society.

Last checked: 31 October 2026

25 gaps: 15 on grammar, 10 on vocabulary. Complete the second half of each word, then check; every answer with its explanation is under the text.

## How vaccines are tested

B2

Before a new vaccine can be given to millions of people, it has to pass several stages of testing. First, i___ is usu___ studied i___ the labor___ and o___ animals. I___ the fi___ results lo___ good, a sm___ group o___ healthy volun___ receives t___ vaccine, a___ researchers ch___ above a___ whether i___ is sa___. In t___ second ph___, several hun___ people ta___ part, a___ the mo___ effective do___ is ident___. Finally, thousands of participants are divided into two groups at random, and neither they nor the doctors know who has received the vaccine and who has been given a placebo.

### Answers and explanations: How vaccines are tested

1. it Grammar
   "it" replaces "the vaccine" (one thing, singular).
2. usually Grammar
   Adverb of frequency between "is" and the participle: "it is usually studied".
3. in Grammar
   "in the laboratory".
4. laboratory Vocabulary
   "laboratory" = a room for scientific experiments.
5. on Grammar
   "on animals": you test something on animals.
6. If Grammar
   "If" introduces a condition.
7. first Vocabulary
   "the first results" = the earliest results.
8. look Vocabulary
   "look good": "look" is followed by an adjective, not an adverb.
9. small Vocabulary
   "a small group" = only a few people.
10. of Grammar
    "a group of volunteers": "of" links the group to its members.
11. volunteers Vocabulary
    "volunteers" = people who agree to take part.
12. the Grammar
    "the vaccine", "the second phase": the thing is known, or fixed by the ordinal number.
13. and Grammar
    Conjunction joining two parts of equal rank.
14. check Vocabulary
    "check whether" = find out if.
15. all Grammar
    "above all" = most importantly.
16. it Grammar
    "it" replaces "the vaccine" (one thing, singular).
17. safe Vocabulary
    "safe" = not dangerous.
18. the Grammar
    "the vaccine", "the second phase": the thing is known, or fixed by the ordinal number.
19. phase Vocabulary
    "phase" = a stage in a process.
20. hundred Grammar
    "several hundred people": no -s on "hundred" after a number or "several".
21. take Vocabulary
    "take part" = participate.
22. and Grammar
    Conjunction joining two parts of equal rank.
23. most Grammar
    "the most effective": long adjectives form the superlative with "most".
24. dose Vocabulary
    "dose" = the amount of a medicine given at one time.
25. identified Grammar
    Passive "is identified": "be" + past participle.

## Tips for B2

- At B2 you meet the passive, relative clauses and linking words such as "however" or "although" more often.
- Watch the word class: adjective or adverb, noun or verb. The start of the word alone is often not enough.
- Keep to about 6 minutes per text, as in the University of Münster C-Test.

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