PLEASE HELP!!! Iodine 131 has a half-life of about 8 days. How long will it take for the radiation of the isotope to go from 100 g to 12.5 g?

Which sentence best describes the relationship between chlorophyll and the chloroplast? a.)chlorophyll is a chemical found in a chloroplast. b.) chloroplast is a chemical found in a chlorophyll. c.) both chlorophyll and chloroplasts are found in animals. d.) both chlorophyll and chloroplasts make carbon dioxide.

The breakdown of food is accomplished by enzymes. a. physical b. chemical c. mechanical d. none of the above

What materials must dams have to produce electricity, and what must occur?