"He wears underwear."
Honestly, I worry maybe some of the advice being given to you might sort of confuse the issue, as thinking of emphasis might be a bit of a simplification in the wrong direction.
In this example, "he" is likely already being spoken of. But don't think of the sentence in terms of emphasis, think of it in terms of the progression of that conversation. Indeed, using は can actually signal a shift of conversational emphasis to the subject, indicating difference with other speakers. So the emphasis can be on "him" doing something differently to others. That's why emphasis might be the wrong way to think about this. Basically, if "he" is being talked about, and is now the conversation topic, use は.
This is neutral, but both "he" and his underwear are important or situationally new, and the emphasis is not on UNDERWEAR but spread out, this new person being spoken of wears/is putting on underwear. In most real-world situations the subject has not become the subject of the conversation yet, and is just coming up. Conversationally, structurally, there is no focus, but the total information is probably directly important.
It seems you might be confused. The polite form is derived from the casual/dictionary form, not the other way around.
There are three types of verbs: いちだん verbs, ごだん verbs and irregular verbs like する and くる.
いちだん verbs end in る, e.g. たべる, and are simple to conjugate. To go from casual to polite form, simply drop the る to get the ます stem, then add ます. For example, casual たべる becomes the stem たべ and then polite たべます.
ごだん verbs end with an u kana (e.g. う, く, す, etc.), e.g. はく. Note that some end in る, similar to いちだん verbs, but they are few; consult a dictionary to check which is which. To go from casual to polite form, replace the final u kana with an i kana (e.g. うto い, く to き, etc.) to get the ます stem, and add ます. For example, casual はく becomes the stem はき and then polite はきます.
Irregular verbs are irregular, so you just need to memorise their conjugations. する becomes します, and くる becomes きます.
Dont Forget ForgetUmbrella's comment.
i've played games in japanese and this information is EXTREMELY important. knowing the difference between the polite form we learned and just putting "る" instead of "ます" is very important to your understand of the actual language. It's casual and can be considered extremely rude if you're speaking to someone who is at a higher social status than you (status ignorance is the biggest form of cursing at people / actual insult in japanese)
Haku is the so called "dictionary form" and is used in casual speech with friends whereas Hakimasu is some present/future tense conjugation that is used in formal situations such as in the workplace or when meeting someone for the first time. I guess Duo focuses on the polite form first because that's the one you're most likely to use if you ever address a Japanese person as a beginner/tourist. However, because they often speak casually, it's good that Duo introduces casual forms as we strengthen our basics along the course. I hope there will be more!
All verbs end with a "u" sound in their basic form. Replacing the "u" with "imasu" (with other changes if the syllable that would created doesn't exist in modern Japanese) makes verbs like this, that don't end in "eru" or "iru", polite. As for why the plain form was used here, it was probably just to give practice with it.
下着 is a better translation, as bras, socks, undershirts, underpants, and long underpants all belong to the category of "underwear"
yeah, instead there's kanji for the plain form of the verb, 履く (haku/はく), which is being used in place of はきます. Even though the "official answer" above uses はきます, it's not the answer Duolingo is expecting. At least they show the new terms on hover.
I'd report this, but they don't seem to offer a way to report it.
Is it not speaking at all, or just saying something different than you remember? If it's the latter, that's because kanji can have several different readings called on'yomi and kun'yomi. As to the former, I've had that happen with both kanji and kana and I assume it's a program problem, but because the kanji will have a balloon pop up with kana, I've never had a problem with it.