The correct sentence is:
Each person’s brain develops and forms new connections, but it is not aware of these changes.
The antecedent of the pronoun "it" is "each person’s brain".
The second one is correct.
Answer: (d) I like trying new activities; therefore, I'm looking forward to learning to snowboard.
Explanation: a conjunctions is a word that joins or connects sentences or phrases, the word "therefore" is an adverb that acts like a conjunction (a conjunctive adverb). When we use words like "therefore", "however", "moreover" etc, to connect to independent clauses, we need to put a semicolon before those words, and a comma after: "I like trying new activities; therefore, I'm looking forward to learning to snowboard.
