"Where are they tonight?"
There is a problem with this exercise. The word tonight implies today-time in English. In Chinese the word is vague. It does not specifically specify today's night. To translate the English into Chinese without adding the word today leaves a sentence open to context. In the context of other sentences the meaning is revealed as today night or a different night or all nights. The sentence is not wrong without the word today it is just left open to context. It is there for more natural to use the sentence without the word today. This also raises the issue of afternoons versus afternoon when translating English to Chinese. It is the same word in Chinese but in English means two different things. A third note to help programmers is to not mark English articles. For example of a doctor and doctors or a brother and brothers or the doctor vs a doctor. My understanding is that Chinese nouns have no plural therefore the English should not be graded when translating Chinese to English and forgetting the article so long as the general meeting is preserved and not falsely changed.