Foreigners often make some strange mistakes in Chinese when they study the most difficult language--- ---Chinese. We try to analyze typical sentences to correct these errors.

          Zuótiān tāmen fǎnɡwèn le yí ɡè ɡōnɡchǎnɡ.
False: 昨天他们访问了一个工厂。
          Zuótiān tāmen cānɡuān le yí ɡè ɡōnɡchǎnɡ.
True: 昨天他们参观了一个工厂。

在汉语里，“访问”指有目的看望某人并谈话，它的宾语大多是人。有时说“访问中国”，意思是不只游览，还要和中国有关人士会谈。句中宾语是“工厂”，主要是看工厂的情况，应改“访问”为“参观”。
In Chinese, 访问 means to visit and talk with someone for a purpose. It usually requires a personal noun as its objects. To say "visit China" implies not only a tour but also talks or discussions with people concerned. The object of the sentence is 工厂 which in fact indicates the state of the factory. 参观 is the matching word for 工厂.