Translation:Il suo maglione
I believe "sweater" can be "maglia" as female or "maglione" as male... what I wonder is why does the sweater have to be male just because the subject of the sentence is male? Does the gender of the sweater determine who is intended to wear it? Is there a gender board in Italy that examines all the seams and cuts of all the sweaters produced and deems them male or female? What if the male subject of this sentence just likes to wear women's clothing? All these questions will never be asked of nouns in the English language, most of which (with exceptions such as countries and ships) are neuter, but in Romantic languages like Italian, they are necessary for Anglophones to ask, I suppose... Or maybe Duolingo just wants us to use the much neglected word "maglione", just in case we've forgotten it exists...