What elemental trying to exist in each row as we move from left to right on a periodic table

The element trend that exists in each row when we move from left to right in the periodic table is going to be that the number of protons increases.

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d. i assume the underlined word is "role." reformat if it isn't.

explanation:

role is closest to part because when replacing words, "playing a vital decision," "playing a vital activity," and "playing a vital dollar" don't make logical sense. the only meaningful choice is "playing a vital part."

this fits one of merriam-webster's definitions of role: "a function or part performed especially in a particular operation or process."

yes he did writing dots to make the answer