The thing is that they teach it from American English, as opposed to British. In our dialect, 'pants' is very correct. I know that 'pants' are underwear to you guys, but that's not the case in America. We have 'trousers', but they're a less-common word for slacks, also known as 'dress pants'. Even then, the term is mostly used by old people. Casual pants are never 'trousers', and jeans are casually lumped in as 'pants'.
I saw that, too. I asked my partner (who is a native speaker of Italian) and he says that it's never "Qual'è", though you're right that they did mark that as correct in an earlier lesson. I had put the same thing you did. Now it's a habit I'll have to break. Thanks Duolingo! ;-)
This link suggests qual'e is archaic (if my interpretation of the Italian is correct!)
I was wondering the same thing. I put "the measurement", which is what DL said la misura meant, and I got it wrong. I mean, I get the translation part of it; when talking about dimensions we typically use phrases like, "the size, the height, the length". When do you ever say "the measurement"? Rarely. I'm sure it's the same everywhere. Just tell us what's right.
"qual/quale" can be translated as "which", meaning "what of these", but in many cases it's used when English still uses "what". I find it hard to explain, but "cosa è" just asks "general information". If you asked "Cosa è la misura?" it would be no different from "Cosa è una misura": you would want to know what a size is.
A man goes to a tailor because he wants a suit. The tailor asks, "Che taglia porta?" (What size are you?). The man says he is unsure because of a recent weight gain. The tailor replies, "Fammi prendere le tue misure" (Let me take your measurements). "Size' is a standard resulting from a measurement, while 'measurement' can be an action or established measuring system determining size(s). A pair of pants may catch your attention. You look at the size on its label, think they will fit, try them on and realize the inseam (its measurement) is not long enough. Apples and oranges.