Correct Answer: C

Rationale: A complex sentence has one independent clause and at least one dependent clause connected by a subordinating conjunction or a relative pronoun. In choice C, the sentence 'Because the distance between stars in the galaxy is far greater than the distance between planets' is a dependent clause introduced by the subordinating conjunction 'Because,' while the rest of the sentence 'interstellar travel is expected to be an even bigger challenge than interplanetary exploration' forms the independent clause. This combination of an independent clause and a dependent clause makes choice C a complex sentence. Choices A, B, and D do not contain both an independent and dependent clause connected in the way that choice C does, thus they do not qualify as complex sentences.

Correct Answer: B

Rationale: The comma following 'Day' is used incorrectly. Commas are typically not used after single-word identifiers like 'Day' in a sentence unless they are part of a list. In this case, the holiday is referred to as 'Parents' Day,' where the apostrophe is used correctly to indicate possession. The comma following 'Day' is unnecessary and should be removed for proper punctuation. Choices A and D both use apostrophes correctly to indicate possession, so they are not incorrect. The comma following 'Congo' in choice C is necessary to set off the introductory phrase 'a public holiday in the Democratic Republic of Congo.' Therefore, the correct answer is B.

Correct Answer: B

Rationale: In sentence B, "Ukrainians" is capitalized because it is referring to a specific group of people, and "Malanka" is also capitalized as it is a holiday name. This follows the rules of capitalization for proper nouns. Choices A, C, and D contain correct capitalization, but they also include additional capitalizations that are unnecessary. For instance, in choice A, "African white-backed vultures" should not be capitalized unless it is part of a proper noun or a title. In choice C, while "Neptune" and "Earth" should be capitalized as they are names of celestial bodies, the word "sun" is not capitalized unless it is used as part of the proper noun "Sun." Choice D correctly capitalizes proper nouns like "Edward Jenner" and "Immunology," but the general terms like "Father" and "vaccine" do not need capitalization unless they are part of a title or a specific name.

Correct Answer: A

Rationale: The correct answer is A: "intra-". The prefix "intra-" is used to indicate that something is inside or within. For example, "intracellular" means within a cell, and "intrapersonal" means within oneself. Choice B, "trans-", typically indicates across, beyond, or through, not inside or within. Choice C, "anti-", is used to indicate against or opposed to. Choice D, "hyper-", usually denotes excessive or above normal levels, not inside or within.

Correct Answer: D

Rationale: The correct plural form of 'potato' is 'potatoes.' In English, most plural nouns form by adding '-es' or simply '-s' to the singular form. Therefore, 'potatoes' is the correctly formed plural noun in this list. The other choices, 'vertebrae,' 'geese,' and 'octopuses,' are the correct plural forms of 'vertebra,' 'goose,' and 'octopus,' respectively. They demonstrate the common rule of adding '-es' or '-s' to form plural nouns.