Correct Answer: A

Rationale: The correct answer is 'A: Past perfect.' In the sentence, 'had been sick' is in the past perfect tense. The past perfect tense is formed with 'had' + the past participle of the main verb. In this sentence, it indicates an action that was completed before another past action. Choices B, C, and D are incorrect because the sentence does not contain the present perfect, past progressive, or present progressive tenses as indicated by the underlined words. The present perfect tense would require 'has' or 'have' + past participle, the past progressive would involve 'was' or 'were' + present participle, and the present progressive would include 'am', 'is', or 'are' + present participle, none of which are present in the sentence.

Correct Answer: C

Rationale: The correct answer is 'C: con-'. The prefix 'con-' means 'with', indicating being together or having a connection. - 'Bio-' means life or living organisms, not 'with'. - 'Per-' means through or completely, not 'with'. - 'Trans-' means across or beyond, not 'with'. Therefore, 'con-' is the only prefix among the options provided that signifies the meaning 'with'.

Correct Answer: B

Rationale: The correct answer is 'I will be unable to come to your party.' This sentence uses formal language by avoiding contractions and employing a more polished wording. Choice A, 'I can't come to your party,' contains a contraction ('can't'), which makes it less formal. Choice C, 'I won't be able to go to your party,' though polite, still uses a contraction ('won't') and is not as formal as the correct answer. Choice D, 'I can't go to your party,' also includes a contraction and is less formal compared to the most formal choice, which is option B.

Correct Answer: C

Rationale: The correct plural of 'century' is 'centuries'. In English, to form the plural of most nouns ending in -y, you change the -y to -ies. Choice A, 'Centurys', is incorrect because it does not follow this rule. Choice B, 'Centures', is also incorrect as it does not provide the correct plural form. Choice D, 'Centuryies', is a completely incorrect and non-standard plural form of 'century'. Therefore, the correct answer is 'Centuries'.

Correct Answer: D

Rationale: The correct conjunction is 'Although.' In this sentence, there is a contrast being made between the difficulty of the class and Allison's success, indicating that despite the class being difficult, she excelled. 'If' implies a condition, 'Since' indicates a reason, and 'Because' shows causation, which do not fit the context of the sentence where a contrast is being expressed.