Read the following article and select the best answer. Article: I once experienced an unforgettable trip to Gloucester to see some of the world's most beautiful and exciting animals in their own habitat , the North Atlantic Ocean. After a long trip by bus, we got on the ship. After a while, we stopped and everyone on the ship started to shout because we saw a humpback whale . It was wonderful. Sometimes, whales came so close to the ship that you thought you could easily touch them. While we were watching the whales, a guide was giving us some information about them. She told us that we saw only two kinds of whales -- 50-foot humpback whales (singing whales) and 70-foot fin back whales (the second largest whales on earth). She also said we could easily recognize a whale by its tail because every whale has a different kind of tail just like people have different fingerprints. They all have names, and on this trip, we saw "Salt" and "Pepper", two whales named by a biologist and a fisherman. They were swimming together all the time. I took twenty-seven photos, but it was very hard to take them because the whales were quick and stayed on the surface of the ocean just for a short time. It was really something. It was one of the chances that a person hardly ever experiences in life, but I had that chance. Question: This passage is mainly about _ . - an unforgettable experience in the forest - an unforgettable trip to see some strange animals in the mountains - a long trip on the ship - an unforgettable trip to watch whales
Answer:
an unforgettable trip to watch whales