Which of the following have completely filled outermost shells?ANonmetalsBMetalsCHalogensDNoble gases

The elements that have completely filled outermost shells are Noble gases (D).

Here's why:

A) Nonmetals: Nonmetals do not have completely filled outermost shells. They tend to gain electrons to achieve a stable electron configuration.

B) Metals: Metals do not have completely filled outermost shells. They tend to lose electrons to achieve a stable electron configuration.

C) Halogens: Halogens do not have completely filled outermost shells. They have seven electrons in their outermost shell and tend to gain one electron to achieve a stable electron configuration.

D) Noble gases: Noble gases have completely filled outermost shells. This is why they are stable and do not readily react with other elements.