can be both an atom and a molecule. A) Hydrogen A) Helium

Hydrogen

Explanation:

Because helium is a noble gas with a full valence shell, it does not bond with other atoms readily. This means that it cannot be a molecule. However, hydrogen can bond with a lot of things, because of its unique property of having just one electron, meaning that it can donate or accept one, making it able to easily become a molecule. Hope this helps!

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.