Correct Answer: C

Rationale: Choice C, 'The dog's tail wagged,' is the correct use of the apostrophe to show possession. In this sentence, the apostrophe is used correctly to indicate that the tail belongs to the dog. Choice A is incorrect as 'it's' is a contraction of 'it is' or 'it has,' not possessive. Choice B is also incorrect as 'Its' should be 'It's' to mean 'It is' or 'It has.' Choice D is incorrect as 'Its'' is grammatically incorrect; the correct form would be 'It's' if it were a contraction or 'Its' if it indicated possession without an apostrophe.

Correct Answer: A

Rationale: The correct answer is A. A compound sentence consists of two independent clauses joined by a conjunction or a semicolon. In sentence A, 'The sky is clear' and 'the stars are bright' are two independent clauses joined by the conjunction 'and.'<br>Choice B is a complex sentence as it has a dependent clause ('Although it was late') and an independent clause ('he stayed up').<br>Choice C is a simple sentence with only one subject and one verb.<br>Choice D is a complex sentence with a dependent clause ('While she reads') and an independent clause ('she listens to music').

Correct Answer: B

Rationale: The correct answer is B because it maintains subject-verb agreement. In this sentence, 'she is' agrees with 'the lead scientist,' and 'does' agrees with 'she.' Choices A, C, and D have subject-verb agreement errors. In choice A, 'write' should be 'writes' to match the singular subject 'The lead scientist,' and 'does' should be 'do' to match the plural 'scientists in the group.' Choice C also has the same subject-verb agreement error as A. In choice D, 'do the research' should be 'does the research' to match the singular 'every scientist in the group.'

Correct Answer: A

Rationale: The sentence about doing yoga is irrelevant to the topic of training for a 5k race. The focus of the paragraph is on the process of preparing for the race through running and training, making sentence A unrelated as it discusses a different physical activity.

Correct Answer: A

Rationale: The correct answer is A: 'Performed by one person.' 'Unilateral' means something done by one person or group without the agreement of another. Choice B is incorrect as it suggests the opposite of what 'unilateral' means. Choice C is incorrect as it does not capture the essence of 'unilateral.' Choice D is incorrect as it is not directly related to the definition of 'unilateral.'