此题不是考查时态，而是考查concern 的“词形变化”（be concerned），由过去分词变来的形容词：be concerned that... 担心......, 后接宾语从句。

这个短语跟be worried that 的用法基本一样。be 的时态应根据宾语从句的时态决定：

We were concerned that few people would speak English, even in Beijing. But we found it common for Chinese people to know a few words of English.

【翻译】我们担心很少有人会说英语，即使在北京也是如此。但是我们发现中国人知道几个英语单词的情况，却是很普遍的。

又如:

1. I was concerned that I was not protected and would get a sunburn.  

我很担心我未作任何防护可能会被晒伤。

来自柯林斯例句

2. Academics and employers are deeply concerned that students are not sufficiently prepared mathematically for university courses.  

学生掌握的数学知识不足以应付大学课程，这让大学老师和用人单位非常担心。

来自柯林斯例句

3. Members are concerned that a merger might mean higher costs, in which case they would oppose it.  

成员们担心合并会导致成本提高，若是那样的话，他们将提出反对。

来自柯林斯例句

4. People were concerned that pets or wildlife could be affected by the pesticides.  

人们担心宠物或野生动物可能受到杀虫剂影响。

来自辞典例句

5. Pentagon brass was concerned that it lacked the firepower to hit it.  

五角大楼的高级官员担忧没有足够的弹药攻击它。

来自辞典例句

6. I am very concerned ( that ) we may not meet the deadline on this.  

我很担心我们可能无法指定时间内完成此事。

来自辞典例句

7. I'm concerned that they may have got lost.  

我担心他们可能迷路了。

来自辞典例句

8. We were concerned that the north slope of the volcano might slide away.  

我们关心的是,火山北坡将会崩塌。

来自辞典例句