Translation:They do not know how to use a compass.
As you know, a/the are the articles in the english grammar which doesn't exist in vietnamese. But vietnamese has classifiers (cái, nước, ngừoi, con, etc).
Their purpose is to classify the following noun. Apart from two syllable words (mostly chinese origin noun) and some very obvious cases, everything must be classified in the vietnamese grammar. The similar pattern in english is for example "three pieces of candy". (where pieces would be the equivivalent of a classifier).
Vietnamese language can tell "the definity" by a determiner (đó/kia/etc), or with something, but it's not built-in in the grammar like articles are in the european languages. Usually the ìnormation is revealed in the context.
On the other hand vietnamese classifiers are built-in in the grammar, while they are not in english.
Let me yet give you some examples with the glossaries:
S: Tôi thích nước cam. T: I like the orange-juice G: i like liquid-type-of orange
Cam is classified as liquid, so we know something about it. Hence we translate the sentence with the article.
S:Tôi thích cam T: I like oranges G: i like orange
The noun is not classified, hence the generalization
S: Tôi thích một nước cam T1: i like an orange juice T2: i like one orange juice G: i like one liquid-type-of orange
The amount of juices is one/1. It is classified, but there is a number before, so it can be any specific (like you don't usually "the" with plural).
Or can it be? How about if there's two particular orange juice that i like?
Tôi thích hai nước cam.
Or maybe in real life you have a determiner (này/đo/kia), which specificies the noun.
Sorry i started to overexplain, im not even native english speaker so i beg my pardon of my possible grammar mistakes. But that's how i understand the matter and the vietnamese mindset...
Haw phu bit lan ten now day zoon LA ban... I understood about half of what was said. Duolingo - can you please have a way of slowing down the speech? Even a little bit slower would help a lot. You do that for Russian, why not this language? Also, an option of choosing someone else's pronunciation the same sentence would help too.