As shown above, どうし, or Verb(Ｖ), is in the sentence-final position in verb sentences. Ｎを represents the direct object(i.e., the word or phrase naming whom or what the action expressed by the verb is done to).
わたしは ラジオを ききます。
I listen to the radio.
The direct object is placed before the verb. わたしは ききます ラジオ is ungrammatical.