If the half life for strontium-90 is approximately 28 years, then what is the whole life for strontium-90? there is no answer choices plz

"water seeps into rock cracks and dissolved minerals there. the solution travels through cracks in the. eventually concentrating into large crystals." which process is that

According ti the following map, what are the most common mineral resources found in the united states?

Which of the following statements best characterizes changes to agriculture in the united states since 1900? a. increased mechanization has reduced the need for labor. b. increased mechanization has increased the need for water, thereby increasing the need for labor. increased mechanization has increased the use of land, thereby increasing the need for labor. d. increased mechanization has increased food production, thereby increasing the need for labor. select the best answer from the choices provided.