Here are the suggested answers for the questions based on the announcement:

**Question 27:**
C. By making small changes in our energy use, we can make a big difference for the environment.

**Question 28:**
A. Last year, we visited Son Doong Cave, which is one of the largest natural caves in the world.

**Question 29:**
B. Construction must be carefully done in progress.

**Question 30:**
C. The Super Weekly Saver ticket can help all travelers to save money.

If you need further assistance, feel free to ask!