I'd say C. The elements one notices exist in the natural world do not last long.
30 ft. Because area = length x width. The first base (5 ft.) x the second base (6ft.)
A some colored families live their lives pretending to be white
John wants the record that was in the box.
A demonstrative pronoun demonstrates where something is. That is used for a singular item which is far away. This is used for a singular item which is close. Those is used for plural items which are far away. These are used for plural items which are close. In this sentence "that" is being used as a demonstrative pronoun. It can stand alone since it is used as the subject of the verb "was".
The sentence "John wants that record" uses "that" as a demonstrative adjective. It comes directly before the noun "record" and demonstrates which record it is.