Here are the suggested answers to your questions:
23. What is the most effective way to combine sentences 1 and 2?
B. Traveling to a new country is both exciting and overwhelming, but it can also be a little bit scary.
This option effectively combines the two ideas while maintaining clarity and proper punctuation.
24. What change needs to be made in sentence 4?
C. Change are to were
This change is needed to maintain consistent past tense throughout the narrative.
25. What change is needed in sentence 9?
C. Insert a comma after however
Adding a comma after "however" improves the sentence's readability, as "however" is an introductory transitional word.