Science question: Which beat summarized the scientific process that led to our current understanding of DNA? 1 each scientist made an important but unrelated contribution
2. Scientists built on the previous work of other scientists to make new discoveries
3 and 4 are too long

2

Explanation:

in terms of cells, it exists from previous existing cells, that means scientist are built up by the work of other scientist

sodium (na), for example, has one electron in its valence shell. this is an unstable state because that valence shell needs eight electrons to be full. in order to fill its valence shell, find a way to add seven electrons to its valence shell