【正确答案】 B

【答案解析】[解析] 必须要提前两周购票。句中purchase：购买。book：预定，如：You'll have to book up early．你要早一点订座。buy：买。sell：卖。obtain：获得，如：I haven't been able to obtain that book．我还没能得到那本书。只有buy意思上和purchase最接近。