Issue Letters 4 in Hindi
There are a couple of issues with Letters 4 on Hindi. In a few of the lessons, it asks you to choose from four answers what word fits in a sentence. Two of the words are the same, but neither of them is correct. I think the correct word has been misplaced with a duplicate answer. Also, on the mobile version, the "ru" with a line over the "u" cannot be matched with the correct letter. Even if they are the last combination left.
The first one is a known issue and a fix will be out soon. Until then, you can temporarily use a workaround by zooming in or using CLM922130's suggestion from this thread-https://forum.duolingo.com/comment/32132245. Further discussion about this can be carried out in that thread.
As for the second issue, would it be possible for you to post a screenshot?