Shipping services were _ strain due to the high volume of mail during the holiday season on top of an ongoing pandemic that was causing known delays.

问题解析

这道题考察的是对句子的理解和词汇的运用。句子的背景是描述在假期季节，由于邮件量大增，加上持续的疫情导致的已知延误，航运服务受到了影响。我们需要选择一个合适的词来填空，使句子通顺且意义明确。

句子结构分析：

• Shipping services：主语，指航运服务。
• were：系动词，表示状态。
• _ strain：空格处需要填一个词，与 strain（压力、紧张）构成一个短语，描述航运服务的状态。
• due to the high volume of mail during the holiday season：原因状语从句，解释为什么航运服务受到影响。
• on top of an ongoing pandemic that was causing known delays：附加原因，进一步解释影响航运服务的因素。

选项分析

根据句子的上下文，我们可以推断空格处需要一个词来描述航运服务受到了压力或紧张。常见的搭配有：

• under strain：处于压力之下。
• in strain：不常用，通常不这样搭配。
• on strain：不常用，通常不这样搭配。

因此，最合适的词是 under。

完整句子

Shipping services were under strain due to the high volume of mail during the holiday season on top of an ongoing pandemic that was causing known delays.

答案

under

解析总结

• under strain 是一个常见的固定搭配，表示“处于压力之下”。
• 句子的背景是假期季节邮件量大增，加上疫情导致的延误，使得航运服务承受了很大的压力。
• 选择 under 使句子通顺且意义明确。