Maria 为一家小型软件公司开展营销，将中型企业作为目标客户。她最近启动了一项通过领英活动广告开展的推广活动。两个月后，数据表现喜人: 展示量和活动注册量都很高。但当她与销售团队碰面时，销售团队表示交易量仍然没有提升。B2B 营销的哪些挑战可以解释 Maria 面临的困境？

The correct answer is "漫长销售周期" (Long sales cycle). In B2B marketing, especially for software targeting medium-sized businesses, the sales cycle is typically extended, often spanning several months or even years. High impressions and event registrations are positive top-of-funnel metrics, but converting these leads into closed deals takes time, nurturing, and multiple touchpoints beyond initial ad engagement. Maria's two-month timeframe is likely insufficient to see a direct impact on sales volume for such a product. "依赖最后触点归因" (Reliance on last-touch attribution) is a challenge but doesn't directly explain the lack of sales volume; it relates to measuring effectiveness. "数据隐私变更" (Data privacy changes) and "系统不兼容性" (System incompatibility) are general B2B challenges but are not directly linked to the scenario of high engagement metrics not yet translating to sales within a short period.