What is an example of an open system

Which popular american sandwich is made by placing a beef patty inside a bun?is an american classic prepared by placing a fried or barbequed beef patty in a bun.

Insulin is a peptide therapeutic used to manage type 1 diabetes, which affects more than 20 million people worldwide according to the international diabetes federation. a significant limitation to the broad distribution and use of insulin to treat type 1 diabetes is the fact that it must be administered by injection rather than orally. why is insulin administered by injection and not orally?

During polarizacion potassium has a blank charge sodium has a blank charge and calcium has a blank charge