Word formation/ families: parts of speech

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Parts of Speech 1:
It is .......... that you wish to change jobs, but the company will be very disappointed to lose you. (UNDERSTAND) --> verb--> adjective

My score is 75 %, the oboved sentense is wrong. Right answer is in red

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Parts of Speech 2:
I got a perfect score: 100%

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I got 6 out of 8 sentences. There are 2 my wrong sentenses:

5. (DO - VERB)That simple mistake meant she managed to .......... all her good work.
--> do --> undo

8. (KIND - ADJECTIVE)My grandmother was one of the .......... people you could ever have met.
--> kindly --> kindest