You can take some 19 to help avoid the discomfort.
答案：(B) preventive measures
語意「你可以採取一些『預防措施』來幫助避免不適」，preventive measures 符合，呼應後文列舉具體建議（選前排座位等）；special opportunities（特殊機會）、potential risks（潛在風險）、significant advantages（顯著優勢）都不合。
measure 你最熟的是動詞「測量」和名詞「尺寸」，所以 take some measures 容易被讀成「做一些測量」。measure 當可數名詞、而且用複數時，意思是措施、對策，take measures 就是「採取措施」。
空格後緊接著 to help avoid the discomfort（來幫助避免不適），已經點明目的是「避免」。再看後面三句：reserve seats where motion is felt the least（訂晃動最小的座位）、Looking out into the distance... can help（望向遠方有幫助）、take medicine before your ride（搭車前先服藥）——列出來的全是事先做、用來預防的動作，所以是 preventive measures（預防措施）。
special opportunities（特殊機會）與 significant advantages（顯著優勢）都是正面的好處，但後面列的是動作不是好處；potential risks（潛在風險）方向相反，你不會「採取風險」來避免不適。
take measures／steps to V（採取措施／步驟來做……）、preventive measures（預防措施）、safety measures（安全措施）、prevent A from Ving（防止 A 做……）、reduce the risk of（降低……的風險）、motion sickness（暈動症）。
If you have ever been sick to your stomach on a rocking boat or a bumpy car ride, you know the discomfort of motion sickness. It can 16 suddenly, progressing from a feeling of uneasiness to a cold sweat. Soon, it can lead to dizziness, nausea, and vomiting.
Motion sickness occurs when the signals your brain receives from your eyes, ears, and body 17 . Your brain doesn't know whether you are stationary or moving when these parts send conflicting information: One part of your balance-sensing system detects that your body is moving, but the other parts 18 . Your brain's confused reaction makes you feel sick. You may experience the discomfort from the motion of cars, boats, or amusement park rides. You may also get sick from playing video games, or looking through a microscope.
You can take some 19 to help avoid the discomfort. If you are traveling, reserve seats where motion is felt the least, such as the front row of a car or forward cars of a train. Looking out into the distance from the vehicle can help 20 . You can also take medicine before your ride to avoid or reduce nausea and vomiting.