Do you mean what is the verb in the sentence ?
Short answer: "That" is used to introduce essential clauses or information, while the pronoun "which" is used to add non-essential or non-defining clauses. Also, these non-essential clauses are set off with commas.
Explanation:
First of all, the words "that" and "which" are both relative pronouns; this means, both introduce clauses that describe a noun previously mentioned. However, the pronoun "that" should be used only to introduce essential or defining clauses (information that cannot be omitted); for example "She is the woman that I love". On the other hand, the word "which" introduces information that is not essential or non-defining clauses; for example "The house, which is located near the sea, is stunning". Moreover, clauses introduced by which are set off in commas to show they are not essential.
The correct answer is A. Think of the rings of a tree trunk: Each planet travels around its own ring, carving out its own path in the solar system.
Explanation:
In writing, making a comparison involves mentioning or describing an element with similar characteristics to better explain an idea. This occurs in the case of "Think of the rings of a tree trunk. Each planet travels around its own ring, carving out its own path in the solar system" because the arrangement of the rings in a trunk is similar to the arrangement of orbital planets, which is the main idea the author tries to describe. Also, the idea planet carves out a specific path in the Solar system follows a ring-like structure help readers understand the movement of planets described in the explanation. Thus, it is in this option there is a comparison to clarify.
