Answer: have improved metalinguistic ability.
Explanation: Metalinguistic skills are the abilities that helps in supporting and managing any language's linguistic factors through control and realization. It gives the freedom of discussing languages who have the understanding and listeners of the language have to be aware to identify the details.
According to the situation mentioned in the question, Henry will get to improve the metalinguisitc ability because he is bilingual person so will display a better understanding for German.
Other options are incorrect because he will face some difficulty if he doesn't listen properly, can find problem in vocabulary and syntax as well and it does not display metalinguisitc mistakes
