"It's not four o'clock now."
ではありません is probably best thought of as 'one' concept (a verb which is the negation of being, polite form). if you wanted to break it down further, で is a copula particle indicating the preceding clause (in this sentence: 四時); は is the topic particle, indicating that the copula is the topic of the following verb, and ありません is the polite negative of ある which is 'to exist', and also indicates that the sentence is present tense (ありません is a compound of ある and the negative suffix -ません）
in this sentence, the second topic particle, in で＜は＞, is a contrastive topic, we are comparing the first topic: 今は with the second topic: 四時では and saying [topic one] isn't [topic two] ありません. This is true even if you omit the thematic topic because it can be understood from context: [今は]四時ではありません。
は is a particle which marks the subject, it's not emphasis. in this case it indicates that 今('now') is the subject of the object (四時; 4 o'clock) and verb (ではありません; it is not)
slightly less formally (and I think actually accepted by this challenge) you can also just say: 四時ではありません。(it is not 4 o’clock [now]; the subject 今(は) can be understood from context)
I'm not sure exactly what part you need help on, but to break it down:
は=particle that marks 'now' as the subject
ではありません= it is not.
So the correct sentence is :今は四時ではありません。
even though ではありません seems like several words, it helps to think of it as one word to be used as the negative form of です.
If you need anymore clarification just let me know and I'll try my best to help!
so, it's probably coincidence but that division is consistent with the parts that make up the lexical phrase. (copula, topic, conjugated part of the "to be" polite suffix negation) But based on other challenges, I think Duolingo just sometimes breaks up the individual hiragana in long strings to remind you how to spell the phrases. (otherwise on the app it'd be easy to get in the habit of recognizing long phrases by just the first few characters)
Am I crazy, or did they mark my right answer incorrect? Screenshot here. https://www.instagram.com/p/B6eJaPvAyHk/?igshid=t1uro3lsb1f7