A recent UN report criticised the use of facial recognition by police in south Wales during a peaceful demonstration as disproportionate and unnecessary.as 这里是介词吗?后边省略了demonstration, 也省略了冠词?
As the world's population continues to grow, the supply of food becomes
more and more of a concern. 老师,您好,请问 of+名词=adj.的这种结构中,名词前面不是通常是零冠词吗?如 of importance =
important,可是为什么上面这个句子中是 of a concern 啊?