The English phrasing might not be as clear and accurate as is needed. Consider the sentence: "They sell black umbrellas, purple umbrellas, and black and purple umbrellas." If we use "They sell black and purple umbrellas", we don't know for certain if they sell single-coloured umbrellas in black or purple or multicoloured black and purple umbrellas, or umbrellas in three different colour choices.
It's good to avoid redundant duplication in English, but avoiding duplication should be balanced with clarity and accuracy in meaning since communication and language is about conveying meaning. A duplicate word isn't redundant if it's used to provide clarity and accuracy.
There is a problem I found in the software. If you use the word bank and make a mistake and then correct it, you will be marked wrong. On this one I switched screens after forgetting the last "umbrellas," came back and selected it. It was marked wrong. So I submit the correct answer but the word back part of the software needs the words to be entered perfectly the first time.