问题补充：
seems to be one of the main reasons for many people in today’s world.
A. Having an adventure; to travel
B. To have an adventure; traveling
C. Have an adventure; to travel
D. To give an adventure; traveling
答案：
(答案→)A. Having an adventure; to travel
B. To have an adventure; traveling
C. Have an adventure; to travel
D. To give an adventure; traveling
解析：seems to be one of the main reasons for many people句中缺少主语，排除C;而不定式作主语表示具体的一次行为，本句是泛指冒险这一行为，所以也排除B和D。选A。
