Which element is most likely to be shiny?
sulfur (s)
boron (b)
calcium (ca)
carbon (c)

calcium is the answer to this question

Calcium (Ca)

Explanation:

Metals have property of being lustrous or shiny. Among the given options, Calcium is metallic in nature. It has atomic number 20 and is alkaline earth metal. Hence, it is most likely to be shiny. Rest, Sulfur (S), Boron (B) and Carbon (C) are non-metals. Non-metals don't possess the property of being shiny.

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.

the correct answer is "inertia"